Pyrrolobenzodiazepine-antibody conjugates

ABSTRACT

Conjugates of an antibody that binds to CD25 with PBD dimers.

The present invention relates to pyrrolobenzodiazepines (PBDs) having a labile C2 or N10 protecting group in the form of a linker to an antibody.

BACKGROUND TO THE INVENTION

Pyrrolobenzodiazepines

Some pyrrolobenzodiazepines (PBDs) have the ability to recognise and bond to specific sequences of DNA; the preferred sequence is PuGPu. The first PBD antitumour antibiotic, anthramycin, was discovered in 1965 (Leimgruber, et al., J. Am. Chem. Soc., 87, 5793-5795 (1965); Leimgruber, et al., J. Am. Chem. Soc., 87, 5791-5793 (1965)). Since then, a number of naturally occurring PBDs have been reported, and over 10 synthetic routes have been developed to a variety of analogues (Thurston, et al., Chem. Rev. 1994, 433-465 (1994); Antonow, D. and Thurston, D. E., Chem. Rev. 2011 111 (4), 2815-2864). Family members include abbeymycin (Hochlowski, et al., J. Antibiotics, 40, 145-148 (1987)), chicamycin (Konishi, et al., J. Antibiotics, 37, 200-206 (1984)), DC-81 (Japanese Patent 58-180 487; Thurston, et al., Chem. Brit., 26, 767-772 (1990); Bose, et al., Tetrahedron, 48, 751-758 (1992)), mazethramycin (Kuminoto, et al., J. Antibiotics, 33, 665-667 (1980)), neothramycins A and B (Takeuchi, et al., J. Antibiotics, 29, 93-96 (1976)), porothramycin (Tsunakawa, et al., J. Antibiotics, 41, 1366-1373 (1988)), prothracarcin (Shimizu, et al, J. Antibiotics, 29, 2492-2503 (1982); Langley and Thurston, J. Org. Chem., 52, 91-97 (1987)), sibanomicin (DC-102) (Hara, et al., J. Antibiotics, 41, 702-704 (1988); Itoh, et al., J. Antibiotics, 41, 1281-1284 (1988)), sibiromycin (Leber, et al., J. Am. Chem. Soc., 110, 2992-2993 (1988)) and tomamycin (Arima, et al., J. Antibiotics, 25, 437-444 (1972)). PBDs are of the general structure:

They differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring there is either an imine (N═C), a carbinolamine (NH—CH(OH)), or a carbinolamine methyl ether (NH—CH(OMe)) at the N10-C11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position which provides them with a right-handed twist when viewed from the C ring towards the A ring. This gives them the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, Acc. Chem. Res., 19, 230-237 (1986)). Their ability to form an adduct in the minor groove, enables them to interfere with DNA processing, hence their use as antitumour agents.

A particularly advantageous pyrrolobenzodiazepine compound is described by Gregson et al. (Chem. Commun. 1999, 797-798) as compound 1, and by Gregson et al. (J. Med. Chem. 2001, 44, 1161-1174) as compound 4a. This compound, also known as SG2000, is shown below:

WO 2007/085930 describes the preparation of dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker is present in the bridge linking the monomer PBD units of the dimer.

The present inventors have described dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody, in WO 2011/130613 and WO 2011/130616. The linker in these compounds is attached to the PBD core via the C2 position, and are generally cleaved by action of an enzyme on the linker group. In WO 2011/130598, the linker in these compounds is attached to one of the available N10 positions on the PBD core, and are generally cleaved by action of an enzyme on the linker group.

Antibody-Drug Conjugates

Antibody therapy has been established for the targeted treatment of patients with cancer, immunological and angiogenic disorders (Carter, P. (2006) Nature Reviews Immunology 6:343-357). The use of antibody-drug conjugates (ADC), i.e. immunoconjugates, for the local delivery of cytotoxic or cytostatic agents, i.e. drugs to kill or inhibit tumor cells in the treatment of cancer, targets delivery of the drug moiety to tumors, and intracellular accumulation therein, whereas systemic administration of these unconjugated drug agents may result in unacceptable levels of toxicity to normal cells (Xie et al (2006) Expert. Opin. Biol. Ther. 6(3):281-291; Kovtun et al (2006) Cancer Res. 66(6):3214-3121; Law et al (2006) Cancer Res. 66(4):2328-2337; Wu et al (2005) Nature Biotech. 23(9):1137-1145; Lambert J. (2005) Current Opin. in Pharmacol. 5:543-549; Hamann P. (2005) Expert Opin. Ther. Patents 15(9):1087-1103; Payne, G. (2003) Cancer Cell 3:207-212; Trail et al (2003) Cancer Immunol. Immunother. 52:328-337; Syrigos and Epenetos (1999) Anticancer Research 19:605-614).

Maximal efficacy with minimal toxicity is sought thereby. Efforts to design and refine ADC have focused on the selectivity of monoclonal antibodies (mAbs) as well as drug mechanism of action, drug-linking, drug/antibody ratio (loading), and drug-releasing properties (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. Nos. 7,521,541; 7,723,485; WO2009/052249; McDonagh (2006) Protein Eng. Design & Sel. 19(7): 299-307; Doronina et al (2006) Bioconj. Chem. 17:114-124; Erickson et al (2006) Cancer Res. 66(8):1-8; Sanderson et al (2005) Clin. Cancer Res. 11:843-852; Jeffrey et al (2005) J. Med. Chem. 48:1344-1358; Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070). Drug moieties may impart their cytotoxic and cytostatic effects by mechanisms including tubulin binding, DNA binding, proteasome and/or topoisomerase inhibition. Some cytotoxic drugs tend to be inactive or less active when conjugated to large antibodies or protein receptor ligands.

The present inventors have developed particular PBD dimer antibody conjugates.

DISCLOSURE OF THE INVENTION

A first aspect of the present invention comprises a conjugate of formula L-(D^(L))_(p), where D^(L) is of formula I or II:

wherein: L is an antibody (Ab) as defined below; when there is a double bond present between C2′ and C3′, R¹² is selected from the group consisting of: (ia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (ib) C₁₋₅ saturated aliphatic alkyl; (ic) C₃₋₆ saturated cycloalkyl; (id)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (ie)

wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (if)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond present between C2′ and C3′, R¹² is

where R^(26a) and R^(26b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; R⁶ and R⁹ are independently selected from H, R, OH, OR, SH, SR, NH₂, NHR, NRR′, nitro, Me₃Sn and halo; where R and R′ are independently selected from optionally substituted C₁₋₁₂ alkyl, C₃₋₂₀ heterocyclyl and C₅₋₂₀ aryl groups; R⁷ is selected from H, R, OH, OR, SH, SR, NH₂, NHR, NHRR′, nitro, Me₃Sn and halo; R″ is a C₃₋₁₂ alkylene group, which chain may be interrupted by one or more heteroatoms, e.g. O, S, NR^(N2) (where R^(N2) is H or C₁₋₄ alkyl), and/or aromatic rings, e.g. benzene or pyridine; Y and Y′ are selected from O, S, or NH; R^(6′), R^(7′), R^(9′) are selected from the same groups as R⁶, R⁷ and R⁹ respectively; [Formula I] R^(L1′) is a linker for connection to the antibody (Ab); R^(11a) is selected from OH, OR^(A), where R^(A) is C₁₋₄ alkyl, and SO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation; R²⁰ and R²¹ either together form a double bond between the nitrogen and carbon atoms to which they are bound or; R²⁰ is selected from H and R^(C), where R^(C) is a capping group; R²¹ is selected from OH, OR^(A) and SO_(z)M; when there is a double bond present between C2 and C3, R² is selected from the group consisting of: (ia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (ib) C₁₋₅ saturated aliphatic alkyl; (ic) C₃₋₆ saturated cycloalkyl; (id)

wherein each of R¹¹, R¹² and R¹³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R² group is no more than 5; (ie)

wherein one of R^(15a) and R^(15b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (if)

where R¹⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond present between C2 and C3, R² is

where R^(16a) and R^(16b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(16a) and R^(16b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; [Formula II] R²² is of formula IIIa, formula IIIb or formula IIIc: (a)

where A is a C₅₋₇ aryl group, and either (i) Q¹ is a single bond, and Q² is selected from a single bond and —Z—(CH₂)_(n)—, where Z is selected from a single bond, O, S and NH and n is from 1 to 3; or (ii) Q¹ is —CH═CH—, and Q² is a single bond; (b)

where; R^(C1), R^(C2) and R^(C3) are independently selected from H and unsubstituted C₁₋₂ alkyl; (c)

where Q is selected from O—R^(L2′), S—R^(L2′) and NR^(N)—R^(L2′), and R^(N) is selected from H, methyl and ethyl X is selected from the group comprising: O—R^(L2′), S—R^(L2′), CO₂—R^(L2′), CO—R^(L2′), NH—C(═O)—R^(L2′), NHNH—R^(L2′), CONHNH—R^(L2′),

NR^(N)R^(L2′), wherein R^(N) is selected from the group comprising H and C₁₋₄ alkyl; R^(L2′) is a linker for connection to the antibody (Ab); R¹⁰ and R¹¹ either together form a double bond between the nitrogen and carbon atoms to which they are bound or; R¹⁰ is H and R¹¹ is selected from OH, OR^(A) and SO_(z)M; R³⁰ and R³¹ either together form a double bond between the nitrogen and carbon atoms to which they are bound or; R³⁰ is H and R³¹ is selected from OH, OR^(A) and SO_(z)M.

In some embodiments, the conjugate is not:

ConjA

ConjB

ConjC:

ConjD

or ConjE:

In other embodiments, it may be preferred that the conjugate is selected from a conjugate of formula ConjA, ConjB, ConjC, ConjD and ConjE.

The subscript p in the formula I is an integer of from 1 to 20. Accordingly, the Conjugates comprise an antibody (Ab) as defined below covalently linked to at least one Drug unit by a Linker unit. The Ligand unit, described more fully below, is a targeting agent that binds to a target moiety. Accordingly, the present invention also provides methods for the treatment of, for example, various cancers and autoimmune disease. The drug loading is represented by p, the number of drug molecules per antibody. Drug loading may range from 1 to 20 Drug units (D^(L)) per antibody. For compositions, p represents the average drug loading of the Conjugates in the composition, and p ranges from 1 to 20.

A second aspect of the invention provides a method of making a conjugate according to the first aspect of the invention comprising conjugating a compound of formula I^(L) or II^(L):

to the antibody (Ab) as defined below, wherein: R^(L1) is a linker suitable for conjugation to the antibody (Ab); R^(22L) is of formula IIIa^(L), formula IIIb^(L) or formula IIIc^(L): (a)

(b)

(c)

where Q^(L) is selected from O—R^(L2), S—R^(L2) and NR^(N)—R^(L2), and R^(N) is selected from H, methyl and ethyl X^(L) is selected from the group comprising: O—R^(L2), S—R^(L2), CO₂—R^(L2), CO—R^(L2), N═C═O—R^(L2), NHNH—R^(L2), CONHNH—R^(L2),

NR^(N)R^(L), wherein R^(N) is selected from the group comprising H and C₁₋₄ alkyl; R^(L2) is a linker suitable for conjugation to the antibody (Ab); and all the remaining groups are as defined in the first aspect.

Thus it may be preferred in the second aspect, that the invention provides a method of making a conjugate selected from the group consisting of ConjA, ConjB, ConjC, ConjD and ConjE comprising conjugating a compound which is selected respectively from A:

B:

C:

D:

and E:

with an antibody as defined below.

WO 2011/130615 discloses compound 26:

which is the parent compound of A. Compound A comprises this PBD with a linker for attachment to a cell binding agent. The cell binding agent provides a number of ethylene glycol moieties to provide solubility which is useful in the synthesis of conjugates.

WO 2010/043380 and WO 2011/130613 disclose compound 30:

WO 2011/130613 also discloses compound 51:

Compound B differs from compound 30 by only having a (CH₂)₃ tether between the PBD moieties, instead of a (CH₂)₅ tether, which reduces the lipophilicity of the released PBD dimer. The linking group is attached to the C2-phenyl group in the para rather than meta position.

WO 2011/130613 discloses compound 93:

Compound C differs from this in two respects. The cell binding agent provides an increased number of ethylene glycol moieties to provide solubility which is useful in the synthesis of conjugates, and the phenyl substituent provide two rather than one oxygen atom, which also aids solubility. Compound C's structure may also mean it binds more strongly in the minor groove.

Compounds A, B and C have two sp² centres in each C-ring, which may allow for stronger binding in the minor groove of DNA, than for compounds with only one sp² centre in each C-ring.

WO 2011/130598 discloses compound 80:

Compound D differs from this by comprising an iodoacetamide group for linking to the cell binding agent. This group may offer advantages over compound 80 with regards to its stability when bound to a cell binding agent (see below). The malemide group in compound 80 can undergo a retro-Michael reaction, becoming unconjugated from the cell binding agent, and thus vulnerable to scavenging by other thiol containing biological molecules, such as albumin and glutathione. Such unconjugation cannot occur with compound A. Also, the iodoacetamide group may avoid other unwanted side reactions.

Compound E differs from previously disclosed PBD dimers with a drug linker having a C2-3 endo-double bond, by having a smaller, less lipophilic C2 substituent, e.g. 4F-phenyl, propylene. As such, the conjugates of compound B (see below) are less likely to aggregate once synthesised. Such aggregation of conjugates can be measured by Size exclusion chromatography (SEC).

Both compound D and E have two sp² centres in each C-ring, which may allow for stronger binding in the minor groove of DNA, than for compounds with only one sp² centre in each C-ring.

The drug linkers disclosed in WO 2010/043880, WO 2011/130613, WO 2011/130598 and WO 2011/130616 may be used in the present invention, and are incorporated herein by reference. The drug linkers described herein may be synthesised as described in these disclosures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows expression of CD25 on Karpas299 and SU-DHL-1 cell lines.

FIG. 2 shows the in vitro efficacy of a conjugate of the invention against SU-DHL-1 cells and Daudi cells.

FIG. 3 shows subcutaneous growth of SU-DHL-1 xenografts in NOD/SCID mice.

FIG. 4 shows the anti-tumour activity of a conjugate of the invention in a SU-DHL-1 xenograft model.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is suitable for use in providing a PBD compound to a preferred site in a subject. The conjugate allows the release of an active PBD compound that does not retain any part of the linker. There is no stub present that could affect the reactivity of the PBD compound. Thus ConjA would release the compound RelA:

ConjB would release the compound RelB:

ConjC would release the compound RelC:

ConjD would release the compound RelD:

and ConjE would release the compound RelE:

The specified link between the PBD dimer and the antibody, in the present invention is preferably stable extracellularly. Before transport or delivery into a cell, the antibody-drug conjugate (ADC) is preferably stable and remains intact, i.e. the antibody remains linked to the drug moiety. The linkers are stable outside the target cell and may be cleaved at some efficacious rate inside the cell. An effective linker will: (i) maintain the specific binding properties of the antibody; (ii) allow intracellular delivery of the conjugate or drug moiety; (iii) remain stable and intact, i.e. not cleaved, until the conjugate has been delivered or transported to its targeted site; and (iv) maintain a cytotoxic, cell-killing effect or a cytostatic effect of the PBD drug moiety. Stability of the ADC may be measured by standard analytical techniques such as mass spectroscopy, HPLC, and the separation/analysis technique LC/MS.

Delivery of the compounds of formulae RelA, RelB, RelC, RelD or RelE is achieved at the desired activation site of the conjugates of formulae ConjA, ConjB, ConjC, ConjD or ConjE by the action of an enzyme, such as cathepsin, on the linking group, and in particular on the valine-alanine dipeptide moiety.

ANTIBODY

In one aspect the antibody is an antibody that binds to CD25, the antibody comprising a VH domain having the sequence according to SEQ ID NO. 1.

The antibody may further comprise a VL domain. In some embodiments the antibody further comprises a VL domain having the sequence according to SEQ ID NO. 2.

In some embodiments the antibody comprises a VH domain paired with a VL domain, the VH and VL domains having the sequences of SEQ ID NO. 1 paired with SEQ ID NO. 2.

The VH and VL domain(s) may pair so as to form an antibody antigen binding site that binds CD25.

In some embodiments the antibody is an intact antibody comprising a VH domain paired with a VL domain, the VH and VL domains having sequences of SEQ ID NO. 1 paired with SEQ ID NO. 2.

In aspect the antibody is an antibody as described herein which has been modified (or further modified) as described below. In some embodiments the antibody is a humanised, deimmunised or resurfaced version of an antibody disclosed herein.

TERMINOLOGY

The term “antibody” herein is used in the broadest sense and specifically covers monoclonal antibodies, polyclonal antibodies, dimers, multimers, multispecific antibodies (e.g., bispecific antibodies), intact antibodies and antibody fragments, so long as they exhibit the desired biological activity, for example, the ability to bind CD25 (Miller et al (2003) Jour. of Immunology 170:4854-4861). Antibodies may be murine, human, humanized, chimeric, or derived from other species. An antibody is a protein generated by the immune system that is capable of recognizing and binding to a specific antigen. (Janeway, C., Travers, P., Walport, M., Shlomchik (2001) Immuno Biology, 5th Ed., Garland Publishing, New York). A target antigen generally has numerous binding sites, also called epitopes, recognized by CDRs on multiple antibodies. Each antibody that specifically binds to a different epitope has a different structure. Thus, one antigen may have more than one corresponding antibody. An antibody includes a full-length immunoglobulin molecule or an immunologically active portion of a full-length immunoglobulin molecule, i.e., a molecule that contains an antigen binding site that immunospecifically binds an antigen of a target of interest or part thereof, such targets including but not limited to, cancer cell or cells that produce autoimmune antibodies associated with an autoimmune disease. The immunoglobulin can be of any type (e.g. IgG, IgE, IgM, IgD, and IgA), class (e.g. IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass, or allotype (e.g. human G1m1, G1m2, G1m3, non-G1m1 [that, is any allotype other than G1m1], G1m17, G2m23, G3m21, G3m28, G3m11, G3m5, G3m13, G3m14, G3m10, G3m15, G3m16, G3m6, G3m24, G3m26, G3m27, A2m1, A2m2, Km1, Km2 and Km3) of immunoglobulin molecule. The immunoglobulins can be derived from any species, including human, murine, or rabbit origin.

As used herein, “binds CD25” is used to mean the antibody binds CD25 with a higher affinity than a non-specific partner such as Bovine Serum Albumin (BSA, Genbank accession no. CAA76847, version no. CAA76847.1 GI:3336842, record update date: Jan. 7, 2011 02:30 PM). In some embodiments the antibody binds CD25 with an association constant (K_(a)) at least 2, 3, 4, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 10⁴, 10⁵ or 10⁶-fold higher than the antibody's association constant for BSA, when measured at physiological conditions. The antibodies of the invention can bind CD25 with a high affinity. For example, in some embodiments the antibody can bind CD25 with a K_(D) equal to or less than about 10⁻⁶ M, such as 1×10⁻⁶, 10⁻⁷, 10⁻⁸, 10⁻⁹, 10⁻¹⁰, 10⁻¹¹, 10⁻¹², 10−¹³ or 10⁻¹⁴.

In some embodiments, CD25 polypeptide corresponds to Genbank accession no. NP_000408, version no. NP_000408.1 GI:4557667, record update date: Sep. 9, 2012 04:59 PM. In one embodiment, the nucleic acid encoding CD25 polypeptide corresponds to Genbank accession no. NM_000417, version no. NM_000417.2 GI:269973860, record update date: Sep. 9, 2012 04:59 PM.

“Antibody fragments” comprise a portion of a full length antibody, generally the antigen binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′)₂, and scFv fragments; diabodies; linear antibodies; fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, CDR (complementary determining region), and epitope-binding fragments of any of the above which immunospecifically bind to cancer cell antigens, viral antigens or microbial antigens, single-chain antibody molecules; and multispecific antibodies formed from antibody fragments.

The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e. the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to polyclonal antibody preparations which include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they may be synthesized uncontaminated by other antibodies. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybridoma method first described by Kohler et al (1975) Nature 256:495, or may be made by recombinant DNA methods (see, U.S. Pat. No. 4,816,567). The monoclonal antibodies may also be isolated from phage antibody libraries using the techniques described in Clackson et al (1991) Nature, 352:624-628; Marks et al (1991) J. Mol. Biol., 222:581-597 or from transgenic mice carrying a fully human immunoglobulin system (Lonberg (2008) Curr. Opinion 20(4):450-459).

The monoclonal antibodies herein specifically include “chimeric” antibodies in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity (U.S. Pat. No. 4,816,567; and Morrison et al (1984) Proc. Natl. Acad. Sci. USA, 81:6851-6855). Chimeric antibodies include “primatized” antibodies comprising variable domain antigen-binding sequences derived from a non-human primate (e.g. Old World Monkey or Ape) and human constant region sequences.

An “intact antibody” herein is one comprising VL and VH domains, as well as a light chain constant domain (CL) and heavy chain constant domains, CH1, CH2 and CH3. The constant domains may be native sequence constant domains (e.g. human native sequence constant domains) or amino acid sequence variant thereof. The intact antibody may have one or more “effector functions” which refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody. Examples of antibody effector functions include C1q binding; complement dependent cytotoxicity; Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; and down regulation of cell surface receptors such as B cell receptor and BCR.

Depending on the amino acid sequence of the constant domain of their heavy chains, intact antibodies can be assigned to different “classes.” There are five major classes of intact antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into “subclasses” (isotypes), e.g., IgG1, IgG2, IgG3, IgG4, IgA, and IgA2. The heavy-chain constant domains that correspond to the different classes of antibodies are called α, δ, Σ, γ, and μ, respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known.

Modification of Antibodies

The antibodies disclosed herein may be modified. For example, to make them less immunogenic to a human subject. This may be achieved using any of a number of techniques familiar to the person skilled in the art. Some of these techniques are described in more detail below.

Humanisation

Techniques to reduce the in vivo immunogenicity of a non-human antibody or antibody fragment include those termed “humanisation”.

A “humanized antibody” refers to a polypeptide comprising at least a portion of a modified variable region of a human antibody wherein a portion of the variable region, preferably a portion substantially less than the intact human variable domain, has been substituted by the corresponding sequence from a non-human species and wherein the modified variable region is linked to at least another part of another protein, preferably the constant region of a human antibody. The expression “humanized antibodies” includes human antibodies in which one or more complementarity determining region (“CDR”) amino acid residues and/or one or more framework region (“FW” or “FR”) amino acid residues are substituted by amino acid residues from analogous sites in rodent or other non-human antibodies. The expression “humanized antibody” also includes an immunoglobulin amino acid sequence variant or fragment thereof that comprises an FR having substantially the amino acid sequence of a human immunoglobulin and a CDR having substantially the amino acid sequence of a non-human immunoglobulin.

“Humanized” forms of non-human (e.g., murine) antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulin. Or, looked at another way, a humanized antibody is a human antibody that also contains selected sequences from non-human (e.g. murine) antibodies in place of the human sequences. A humanized antibody can include conservative amino acid substitutions or non-natural residues from the same or different species that do not significantly alter its binding and/or biologic activity. Such antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulins.

There are a range of humanisation techniques, including ‘CDR grafting’, ‘guided selection’, ‘deimmunization’, ‘resurfacing’ (also known as ‘veneering’), ‘composite antibodies’, ‘Human String Content Optimisation’ and framework shuffling.

CDR Grafting

In this technique, the humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary-determining region (CDR) of the recipient antibody are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, camel, bovine, goat, or rabbit having the desired properties (in effect, the non-human CDRs are ‘grafted’ onto the human framework). In some instances, framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues (this may happen when, for example, a particular FR residue has significant effect on antigen binding).

Furthermore, humanized antibodies can comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. These modifications are made to further refine and maximize antibody performance. Thus, in general, a humanized antibody will comprise all of at least one, and in one aspect two, variable domains, in which all or all of the hypervariable loops correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), or that of a human immunoglobulin.

Guided Selection

The method consists of combining the V_(H) or V_(L) domain of a given non-human antibody specific for a particular epitope with a human V_(H) or V_(L) library and specific human V domains are selected against the antigen of interest. This selected human VH is then combined with a VL library to generate a completely human VH×VL combination. The method is described in Nature Biotechnology (N.Y.) 12, (1994) 899-903.

Composite Antibodies

In this method, two or more segments of amino acid sequence from a human antibody are combined within the final antibody molecule. They are constructed by combining multiple human VH and VL sequence segments in combinations which limit or avoid human T cell epitopes in the final composite antibody V regions. Where required, T cell epitopes are limited or avoided by, exchanging V region segments contributing to or encoding a T cell epitope with alternative segments which avoid T cell epitopes. This method is described in US 2008/0206239 A1.

Deimmunization

This method involves the removal of human (or other second species) T-cell epitopes from the V regions of the therapeutic antibody (or other molecule). The therapeutic antibodies V-region sequence is analyzed for the presence of MHC class II-binding motifs by, for example, comparison with databases of MHC-binding motifs (such as the “motifs” database available on the website of the Walter+Eliza Hall Institute of Medical Research). Alternatively, MHC class II-binding motifs may be identified using computational threading methods such as those devised by Altuvia et al. (J. Mol. Biol. 249 244-250 (1995)); in these methods, consecutive overlapping peptides from the V-region sequences are tested for their binding energies to MHC class II proteins. This data can then be combined with information on other sequence features which relate to successfully presented peptides, such as amphipathicity, Rothbard motifs, and cleavage sites for cathepsin B and other processing enzymes.

Once potential second species (e.g. human) T-cell epitopes have been identified, they are eliminated by the alteration of one or more amino acids. The modified amino acids are usually within the T-cell epitope itself, but may also be adjacent to the epitope in terms of the primary or secondary structure of the protein (and therefore, may not be adjacent in the primary structure). Most typically, the alteration is by way of substitution but, in some circumstances amino acid addition or deletion will be more appropriate.

All alterations can be accomplished by recombinant DNA technology, so that the final molecule may be prepared by expression from a recombinant host using well established methods such as Site Directed Mutagenesis. However, the use of protein chemistry or any other means of molecular alteration is also possible.

Resurfacing

This method involves:

-   -   (a) determining the conformational structure of the variable         region of the non-human (e.g. rodent) antibody (or fragment         thereof) by constructing a three-dimensional model of the         non-human antibody variable region;     -   (b) generating sequence alignments using relative accessibility         distributions from x-ray crystallographic structures of a         sufficient number of non-human and human antibody variable         region heavy and light chains to give a set of heavy and light         chain framework positions wherein the alignment positions are         identical in 98% of the sufficient number of non-human antibody         heavy and light chains;     -   (c) defining for the non-human antibody to be humanized, a set         of heavy and light chain surface exposed amino acid residues         using the set of framework positions generated in step (b);     -   (d) identifying from human antibody amino acid sequences a set         of heavy and light chain surface exposed amino acid residues         that is most closely identical to the set of surface exposed         amino acid residues defined in step (c), wherein the heavy and         light chain from the human antibody are or are not naturally         paired;     -   (e) substituting, in the amino acid sequence of the non-human         antibody to be humanized, the set of heavy and light chain         surface exposed amino acid residues defined in step (c) with the         set of heavy and light chain surface exposed amino acid residues         identified in step (d);     -   (f) constructing a three-dimensional model of the variable         region of the non-human antibody resulting from the substituting         specified in step (e);     -   (g) identifying, by comparing the three-dimensional models         constructed in steps (a) and (f), any amino acid residues from         the sets identified in steps (c) or (d), that are within 5         Angstroms of any atom of any residue of the complementarity         determining regions of the non-human antibody to be humanized;         and     -   (h) changing any residues identified in step (g) from the human         to the original non-human amino acid residue to thereby define a         non-human antibody humanizing set of surface exposed amino acid         residues; with the proviso that step (a) need not be conducted         first, but must be conducted prior to step (g).         Superhumanization

The method compares the non-human sequence with the functional human germline gene repertoire. Those human genes encoding canonical structures identical or closely related to the non-human sequences are selected. Those selected human genes with highest homology within the CDRs are chosen as FR donors. Finally, the non-human CDRs are grafted onto these human FRs. This method is described in patent WO 2005/079479 A2.

Human String Content Optimization

This method compares the non-human (e.g. mouse) sequence with the repertoire of human germline genes and the differences are scored as Human String Content (HSC) that quantifies a sequence at the level of potential MHC/T-cell epitopes. The target sequence is then humanized by maximizing its HSC rather than using a global identity measure to generate multiple diverse humanized variants (described in Molecular Immunology, 44, (2007) 1986-1998).

Framework Shuffling

The CDRs of the non-human antibody are fused in-frame to cDNA pools encompassing all known heavy and light chain human germline gene frameworks. Humanised antibodies are then selected by e.g. panning of the phage displayed antibody library. This is described in Methods 36, 43-60 (2005).

DEFINITIONS

Pharmaceutically Acceptable Cations

Examples of pharmaceutically acceptable monovalent and divalent cations are discussed in Berge, et al., J. Pharm. Sci., 66, 1-19 (1977), which is incorporated herein by reference.

The pharmaceutically acceptable cation may be inorganic or organic.

Examples of pharmaceutically acceptable monovalent inorganic cations include, but are not limited to, alkali metal ions such as Na⁺ and K⁺. Examples of pharmaceutically acceptable divalent inorganic cations include, but are not limited to, alkaline earth cations such as Ca²⁺ and Mg²⁺. Examples of pharmaceutically acceptable organic cations include, but are not limited to, ammonium ion (i.e. NH₄ ⁺) and substituted ammonium ions (e.g. NH₃R⁺, NH₂R₂ ⁺, NHR₃ ⁺, NR₄ ⁺). Examples of some suitable substituted ammonium ions are those derived from: ethylamine, diethylamine, dicyclohexylamine, triethylamine, butylamine, ethylenediamine, ethanolamine, diethanolamine, piperazine, benzylamine, phenylbenzylamine, choline, meglumine, and tromethamine, as well as amino acids, such as lysine and arginine. An example of a common quaternary ammonium ion is N(CH₃)₄ ⁺.

Substituents

The phrase “optionally substituted” as used herein, pertains to a parent group which may be unsubstituted or which may be substituted.

Unless otherwise specified, the term “substituted” as used herein, pertains to a parent group which bears one or more substituents. The term “substituent” is used herein in the conventional sense and refers to a chemical moiety which is covalently attached to, or if appropriate, fused to, a parent group. A wide variety of substituents are well known, and methods for their formation and introduction into a variety of parent groups are also well known.

Examples of substituents are described in more detail below.

C₁₋₁₂ alkyl: The term “C₁₋₁₂ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 12 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). The term “C₁₋₄ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 4 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). Thus, the term “alkyl” includes the sub-classes alkenyl, alkynyl, cycloalkyl, etc., discussed below.

Examples of saturated alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), propyl (C₃), butyl (C₄), pentyl (C₅), hexyl (C₆) and heptyl (C₇).

Examples of saturated linear alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), n-propyl (C₃), n-butyl (C₄), n-pentyl (amyl) (C₅), n-hexyl (C₆) and n-heptyl (C₇).

Examples of saturated branched alkyl groups include iso-propyl (C₃), iso-butyl (C₄), sec-butyl (C₄), tert-butyl (C₄), iso-pentyl (C₅), and neo-pentyl (C₅).

C₂₋₁₂ Alkenyl: The term “C₂₋₁₂ alkenyl” as used herein, pertains to an alkyl group having one or more carbon-carbon double bonds.

Examples of unsaturated alkenyl groups include, but are not limited to, ethenyl (vinyl, —CH═CH₂), 1-propenyl (—CH═CH—CH₃), 2-propenyl (allyl, —CH—CH═CH₂), isopropenyl (1-methylvinyl, —C(CH₃)═CH₂), butenyl (C₄), pentenyl (C₅), and hexenyl (C₆).

C₂₋₁₂ alkynyl: The term “C₂₋₁₂ alkynyl” as used herein, pertains to an alkyl group having one or more carbon-carbon triple bonds.

Examples of unsaturated alkynyl groups include, but are not limited to, ethynyl (—C≡CH) and 2-propynyl (propargyl, —CH₂—C≡CH).

C₃₋₁₂ cycloalkyl: The term “C₃₋₁₂ cycloalkyl” as used herein, pertains to an alkyl group which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a cyclic hydrocarbon (carbocyclic) compound, which moiety has from 3 to 7 carbon atoms, including from 3 to 7 ring atoms.

Examples of cycloalkyl groups include, but are not limited to, those derived from:

-   -   saturated monocyclic hydrocarbon compounds:         cyclopropane (C₃), cyclobutane (C₄), cyclopentane (C₅),         cyclohexane (C₆), cycloheptane (C₇), methylcyclopropane (C₄),         dimethylcyclopropane (C₅), methylcyclobutane (C₅),         dimethylcyclobutane (C₆), methylcyclopentane (C₆),         dimethylcyclopentane (C₇) and methylcyclohexane (C₇);     -   unsaturated monocyclic hydrocarbon compounds:         cyclopropene (C₃), cyclobutene (C₄), cyclopentene (C₅),         cyclohexene (C₆), methylcyclopropene (C₄), dimethylcyclopropene         (C₅), methylcyclobutene (C₅), dimethylcyclobutene (C₆),         methylcyclopentene (C₆), dimethylcyclopentene (C₇) and         methylcyclohexene (C₇); and     -   saturated polycyclic hydrocarbon compounds:         norcarane (C₇), norpinane (C₇), norbornane (C₇).

C₃₋₂₀ heterocyclyl: The term “C₃₋₂₀ heterocyclyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₃₋₇, C₅₋₆, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆heterocyclyl”, as used herein, pertains to a heterocyclyl group having 5 or 6 ring atoms.

Examples of monocyclic heterocyclyl groups include, but are not limited to, those derived from:

N₁: aziridine (C₃), azetidine (C₄), pyrrolidine (tetrahydropyrrole) (C₅), pyrroline (e.g., 3-pyrroline, 2,5-dihydropyrrole) (C₅), 2H-pyrrole or 3H-pyrrole (isopyrrole, isoazole) (C₅), piperidine (C₆), dihydropyridine (C₆), tetrahydropyridine (C₆), azepine (C₇); O₁: oxirane (C₃), oxetane (C₄), oxolane (tetrahydrofuran) (C₅), oxole (dihydrofuran) (C₅), oxane (tetrahydropyran) (C₆), dihydropyran (C₆), pyran (C₆), oxepin (C₇); S₁: thiirane (C₃), thietane (C₄), thiolane (tetrahydrothiophene) (C₅), thiane (tetrahydrothiopyran) (C₆), thiepane (C₇); O₂: dioxolane (C₅), dioxane (C₆), and dioxepane (C₇); O₃: trioxane (C₆); N₂: imidazolidine (C₅), pyrazolidine (diazolidine) (C₅), imidazoline (C₅), pyrazoline (dihydropyrazole) (C₅), piperazine (C₆); N₁O₁: tetrahydrooxazole (C₅), dihydrooxazole (C₅), tetrahydroisoxazole (C₅), dihydroisoxazole (C₅), morpholine (C₆), tetrahydrooxazine (C₆), dihydrooxazine (C₆), oxazine (C₆); N₁S₁: thiazoline (C₅), thiazolidine (C₅), thiomorpholine (C₆); N₂O₁: oxadiazine (C₆); O₁S₁: oxathiole (C₅) and oxathiane (thioxane) (C₆); and, N₁O₁S₁: oxathiazine (C₆).

Examples of substituted monocyclic heterocyclyl groups include those derived from saccharides, in cyclic form, for example, furanoses (C₅), such as arabinofuranose, lyxofuranose, ribofuranose, and xylofuranse, and pyranoses (C₆), such as allopyranose, altropyranose, glucopyranose, mannopyranose, gulopyranose, idopyranose, galactopyranose, and talopyranose.

C₅₋₂₀ aryl: The term “C₅₋₂₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 3 to 20 ring atoms. The term “C₅₋₇ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 7 ring atoms and the term “C₅₋₁₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 10 ring atoms. Preferably, each ring has from 5 to 7 ring atoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₅₋₇, C₅₋₆, C₅₋₁₀, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆ aryl” as used herein, pertains to an aryl group having 5 or 6 ring atoms.

The ring atoms may be all carbon atoms, as in “carboaryl groups”.

Examples of carboaryl groups include, but are not limited to, those derived from benzene (i.e. phenyl) (C₆), naphthalene (C₁₀), azulene (C₁₀), anthracene (C₁₄), phenanthrene (C₁₄), naphthacene (C₁₈), and pyrene (C₁₆).

Examples of aryl groups which comprise fused rings, at least one of which is an aromatic ring, include, but are not limited to, groups derived from indane (e.g. 2,3-dihydro-1H-indene) (C₉), indene (C₉), isoindene (C₉), tetraline (1,2,3,4-tetrahydronaphthalene (C₁₀), acenaphthene (C₁₂), fluorene (C₁₃), phenalene (C₁₃), acephenanthrene (C₁₅), and aceanthrene (C₁₆).

Alternatively, the ring atoms may include one or more heteroatoms, as in “heteroaryl groups”. Examples of monocyclic heteroaryl groups include, but are not limited to, those derived from:

N₁: pyrrole (azole) (C₅), pyridine (azine) (C₆);

O₁: furan (oxole) (C₅);

S₁: thiophene (thiole) (C₅);

N₁O₁: oxazole (C₅), isoxazole (C₅), isoxazine (C₆);

N₂O₁: oxadiazole (furazan) (C₅);

N₃O₁: oxatriazole (C₅);

N₁S₁: thiazole (C₅), isothiazole (C₅);

N₂: imidazole (1,3-diazole) (C₅), pyrazole (1,2-diazole) (C₅), pyridazine (1,2-diazine) (C₆), pyrimidine (1,3-diazine) (C₆) (e.g., cytosine, thymine, uracil), pyrazine (1,4-diazine) (C₆);

N₃: triazole (C₅), triazine (C₆); and,

N₄: tetrazole (C₅).

Examples of heteroaryl which comprise fused rings, include, but are not limited to:

-   -   C₉ (with 2 fused rings) derived from benzofuran (O₁),         isobenzofuran (O₁), indole (N₁), isoindole (N₁), indolizine         (N₁), indoline (N₁), isoindoline (N₁), purine (N₄) (e.g.,         adenine, guanine), benzimidazole (N₂), indazole (N₂),         benzoxazole (N₁O₁), benzisoxazole (N₁O₁), benzodioxole (O₂),         benzofurazan (N₂O₁), benzotriazole (N₃), benzothiofuran (S₁),         benzothiazole (N₁S₁), benzothiadiazole (N₂S);     -   C₁₀ (with 2 fused rings) derived from chromene (O₁), isochromene         (O₁), chroman (O₁), isochroman (O₁), benzodioxan (O₂), quinoline         (N₁), isoquinoline (N₁), quinolizine (N₁), benzoxazine (N₁O₁),         benzodiazine (N₂), pyridopyridine (N₂), quinoxaline (N₂),         quinazoline (N₂), cinnoline (N₂), phthalazine (N₂),         naphthyridine (N₂), pteridine (N₄);     -   C₁₁ (with 2 fused rings) derived from benzodiazepine (N₂);     -   C₁₃ (with 3 fused rings) derived from carbazole (N₁),         dibenzofuran (O₁), dibenzothiophene (S₁), carboline (N₂),         perimidine (N₂), pyridoindole (N₂); and,     -   C₁₄ (with 3 fused rings) derived from acridine (N₁), xanthene         (O₁), thioxanthene (S₁), oxanthrene (O₂), phenoxathiin (O₁S₁),         phenazine (N₂), phenoxazine (N₁O₁), phenothiazine (N₁S₁),         thianthrene (S₂), phenanthridine (N₁), phenanthroline (N₂),         phenazine (N₂).

The above groups, whether alone or part of another substituent, may themselves optionally be substituted with one or more groups selected from themselves and the additional substituents listed below.

Halo: —F, —Cl, —Br, and —I.

Hydroxy: —OH.

Ether: —OR, wherein R is an ether substituent, for example, a C₁₋₇ alkyl group (also referred to as a C₁₋₇ alkoxy group, discussed below), a C₃₋₂₀ heterocyclyl group (also referred to as a C₃₋₂₀ heterocyclyloxy group), or a C₅₋₂₀ aryl group (also referred to as a C₅₋₂₀ aryloxy group), preferably a C₁₋₇alkyl group. Alkoxy: —OR, wherein R is an alkyl group, for example, a C₁₋₇ alkyl group. Examples of C₁₋₇ alkoxy groups include, but are not limited to, —OMe (methoxy), —OEt (ethoxy), —O(nPr) (n-propoxy), —O(iPr) (isopropoxy), —O(nBu) (n-butoxy), —O(sBu) (sec-butoxy), —O(iBu) (isobutoxy), and —O(tBu) (tert-butoxy). Acetal: —CH(OR¹)(OR²), wherein R¹ and R² are independently acetal substituents, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group, or, in the case of a “cyclic” acetal group, R¹ and R², taken together with the two oxygen atoms to which they are attached, and the carbon atoms to which they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Examples of acetal groups include, but are not limited to, —CH(OMe)₂, —CH(OEt)₂, and —CH(OMe)(OEt). Hemiacetal: —CH(OH)(OR¹), wherein R¹ is a hemiacetal substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of hemiacetal groups include, but are not limited to, —CH(OH)(OMe) and —CH(OH)(OEt). Ketal: —CR(OR¹)(OR²), where R¹ and R² are as defined for acetals, and R is a ketal substituent other than hydrogen, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples ketal groups include, but are not limited to, —C(Me)(OMe)₂, —C(Me)(OEt)₂, —C(Me)(OMe)(OEt), —C(Et)(OMe)₂, —C(Et)(OEt)₂, and —C(Et)(OMe)(OEt). Hemiketal: —CR(OH)(OR¹), where R¹ is as defined for hemiacetals, and R is a hemiketal substituent other than hydrogen, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of hemiacetal groups include, but are not limited to, —C(Me)(OH)(OMe), —C(Et)(OH)(OMe), —C(Me)(OH)(OEt), and —C(Et)(OH)(OEt). Oxo (keto, -one): ═O. Thione (thioketone): ═S. Imino (imine): ═NR, wherein R is an imino substituent, for example, hydrogen, C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably hydrogen or a C₁₋₇ alkyl group. Examples of ester groups include, but are not limited to, ═NH, ═NMe, ═NEt, and ═NPh. Formyl (carbaldehyde, carboxaldehyde): —C(═O)H. Acyl (keto): —C(═O)R, wherein R is an acyl substituent, for example, a C₁₋₇ alkyl group (also referred to as C₁₋₇ alkylacyl or C₁₋₇ alkanoyl), a C₃₋₂₀ heterocyclyl group (also referred to as C₃₋₂₀ heterocyclylacyl), or a C₅₋₂₀ aryl group (also referred to as C₅₋₂₀ arylacyl), preferably a C₁₋₇ alkyl group. Examples of acyl groups include, but are not limited to, —C(═O)CH₃ (acetyl), —C(═O)CH₂CH₃ (propionyl), —C(═O)C(CH₃)₃ (t-butyryl), and —C(═O)Ph (benzoyl, phenone). Carboxy (carboxylic acid): —C(═O)OH. Thiocarboxy (thiocarboxylic acid): —C(═S)SH. Thiolocarboxy (thiolocarboxylic acid): —C(═O)SH. Thionocarboxy (thionocarboxylic acid): —C(═S)OH. Imidic acid: —C(═NH)OH. Hydroxamic acid: —C(═NOH)OH. Ester (carboxylate, carboxylic acid ester, oxycarbonyl): —C(═O)OR, wherein R is an ester substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of ester groups include, but are not limited to, —C(═O)OCH₃, —C(═O)OCH₂CH₃, —C(═O)OC(CH₃)₃, and —C(═O)OPh. Acyloxy (reverse ester): —OC(═O)R, wherein R is an acyloxy substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of acyloxy groups include, but are not limited to, —OC(═O)CH₃ (acetoxy), —OC(═O)CH₂CH₃, —OC(═O)C(CH₃)₃, —OC(═O)Ph, and —OC(═O)CH₂Ph. Oxycarboyloxy: —OC(═O)OR, wherein R is an ester substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of ester groups include, but are not limited to, —OC(═O)OCH₃, —OC(═O)OCH₂CH₃, —OC(═O)OC(CH₃)₃, and —OC(═O)OPh. Amino: —NR¹R², wherein R¹ and R² are independently amino substituents, for example, hydrogen, a C₁₋₇ alkyl group (also referred to as C₁₋₇ alkylamino or di-C₁₋₇ alkylamino), a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇ alkyl group, or, in the case of a “cyclic” amino group, R¹ and R², taken together with the nitrogen atom to which they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Amino groups may be primary (—NH₂), secondary (—NHR¹), or tertiary (—NHR¹R²), and in cationic form, may be quaternary (—+NR¹R²R³). Examples of amino groups include, but are not limited to, —NH₂, —NHCH₃, —NHC(CH₃)₂, —N(CH₃)₂, —N(CH₂CH₃)₂, and —NHPh. Examples of cyclic amino groups include, but are not limited to, aziridino, azetidino, pyrrolidino, piperidino, piperazino, morpholino, and thiomorpholino. Amido (carbamoyl, carbamyl, aminocarbonyl, carboxamide): —C(═O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited to, —C(═O)NH₂, —C(═O)NHCH₃, —C(═O)N(CH₃)₂, —C(═O)NHCH₂CH₃, and —C(═O)N(CH₂CH₃)₂, as well as amido groups in which R¹ and R², together with the nitrogen atom to which they are attached, form a heterocyclic structure as in, for example, piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and piperazinocarbonyl. Thioamido (thiocarbamyl): —C(═S)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited to, —C(═S)NH₂, —C(═S)NHCH₃, —C(═S)N(CH₃)₂, and —C(═S)NHCH₂CH₃. Acylamido (acylamino): —NR¹C(═O)R², wherein R¹ is an amide substituent, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably hydrogen or a C₁₋₇ alkyl group, and R² is an acyl substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀aryl group, preferably hydrogen or a C₁₋₇ alkyl group. Examples of acylamide groups include, but are not limited to, —NHC(═O)CH₃, —NHC(═O)CH₂CH₃, and —NHC(═O)Ph. R¹ and R² may together form a cyclic structure, as in, for example, succinimidyl, maleimidyl, and phthalimidyl:

Aminocarbonyloxy: —OC(═O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of aminocarbonyloxy groups include, but are not limited to, —OC(═O)NH₂, —OC(═O)NHMe, —OC(═O)NMe₂, and —OC(═O)NEt₂. Ureido: —N(R¹)CONR²R³ wherein R² and R³ are independently amino substituents, as defined for amino groups, and R¹ is a ureido substituent, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably hydrogen or a C₁₋₇ alkyl group. Examples of ureido groups include, but are not limited to, —NHCONH₂, —NHCONHMe, —NHCONHEt, —NHCONMe₂, —NHCONEt₂, —NMeCONH₂, —NMeCONHMe, —NMeCONHEt, —NMeCONMe₂, and —NMeCONEt₂. Guanidino: —NH—C(═NH)NH₂. Tetrazolyl: a five membered aromatic ring having four nitrogen atoms and one carbon atom,

Imino: ═NR, wherein R is an imino substituent, for example, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇alkyl group. Examples of imino groups include, but are not limited to, ═NH, ═NMe, and ═NEt. Amidine (amidino): —C(═NR)NR₂, wherein each R is an amidine substituent, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇ alkyl group. Examples of amidine groups include, but are not limited to, —C(═NH)NH₂, —C(═NH)NMe₂, and —C(═NMe)NMe₂. Nitro: —NO₂. Nitroso: —NO. Azido: —N₃. Cyano (nitrile, carbonitrile): —CN. Isocyano: —NC. Cyanato: —OCN. Isocyanato: —NCO. Thiocyano (thiocyanato): —SCN. Isothiocyano (isothiocyanato): —NCS. Sulfhydryl (thiol, mercapto): —SH. Thioether (sulfide): —SR, wherein R is a thioether substituent, for example, a C₁₋₇ alkyl group (also referred to as a C₁₋₇alkylthio group), a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of C₁₋₇ alkylthio groups include, but are not limited to, —SCH₃ and —SCH₂CH₃. Disulfide: —SS—R, wherein R is a disulfide substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group (also referred to herein a C₁₋₇ alkyl disulfide). Examples of C₁₋₇ alkyl disulfide groups include, but are not limited to, —SSCH₃ and —SSCH₂CH₃. Sulfine (sulfinyl, sulfoxide): —S(═O)R, wherein R is a sulfine substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfine groups include, but are not limited to, —S(═O)CH₃ and —S(═O)CH₂CH₃. Sulfone (sulfonyl): —S(═O)₂R, wherein R is a sulfone substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group, including, for example, a fluorinated or perfluorinated C₁₋₇ alkyl group. Examples of sulfone groups include, but are not limited to, —S(═O)₂CH₃ (methanesulfonyl, mesyl), —S(═O)₂CF₃ (triflyl), —S(═O)₂CH₂CH₃ (esyl), —S(═O)₂C₄F₉ (nonaflyl), —S(═O)₂CH₂CF₃ (tresyl), —S(═O)₂CH₂CH₂NH₂ (tauryl), —S(═O)₂Ph (phenylsulfonyl, besyl), 4-methylphenylsulfonyl (tosyl), 4-chlorophenylsulfonyl (closyl), 4-bromophenylsulfonyl (brosyl), 4-nitrophenyl (nosyl), 2-naphthalenesulfonate (napsyl), and 5-dimethylamino-naphthalen-1-ylsulfonate (dansyl). Sulfinic acid (sulfino): —S(═O)OH, —SO₂H. Sulfonic acid (sulfo): —S(═O)₂OH, —SO₃H. Sulfinate (sulfinic acid ester): —S(═O)OR; wherein R is a sulfinate substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfinate groups include, but are not limited to, —S(═O)OCH₃ (methoxysulfinyl; methyl sulfinate) and —S(═O)OCH₂CH₃ (ethoxysulfinyl; ethyl sulfinate). Sulfonate (sulfonic acid ester): —S(═O)₂OR, wherein R is a sulfonate substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfonate groups include, but are not limited to, —S(═O)₂CH₃ (methoxysulfonyl; methyl sulfonate) and —S(═O)₂CH₂CH₃ (ethoxysulfonyl; ethyl sulfonate). Sulfinyloxy: —OS(═O)R, wherein R is a sulfinyloxy substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfinyloxy groups include, but are not limited to, —OS(═O)CH₃ and —OS(═O)CH₂CH₃. Sulfonyloxy: —OS(═O)₂R, wherein R is a sulfonyloxy substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfonyloxy groups include, but are not limited to, —OS(═O)₂CH₃ (mesylate) and —OS(═O)₂CH₂CH₃ (esylate). Sulfate: —OS(═O)₂OR; wherein R is a sulfate substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfate groups include, but are not limited to, —OS(═O)₂OCH₃ and —SO(═O)₂OCH₂CH₃. Sulfamyl (sulfamoyl; sulfinic acid amide; sulfinamide): —S(═O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of sulfamyl groups include, but are not limited to, —S(═O)NH₂, —S(═O)NH(CH₃), —S(═O)N(CH₃)₂, —S(═O)NH(CH₂CH₃), —S(═O)N(CH₂CH₃)₂, and —S(═O)NHPh. Sulfonamido (sulfinamoyl; sulfonic acid amide; sulfonamide): —S(═O)₂NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of sulfonamido groups include, but are not limited to, —S(═O)₂NH₂, —S(═O)₂NH(CH₃), —S(═O)₂N(CH₃)₂, —S(═O)₂NH(CH₂CH₃), —S(═O)₂N(CH₂CH₃)₂, and —S(═O)₂NHPh. Sulfamino: —NR¹S(═O)₂OH, wherein R¹ is an amino substituent, as defined for amino groups. Examples of sulfamino groups include, but are not limited to, —NHS(═O)₂OH and —N(CH₃)S(═O)₂OH. Sulfonamino: —NR¹S(═O)₂R, wherein R¹ is an amino substituent, as defined for amino groups, and R is a sulfonamino substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfonamino groups include, but are not limited to, —NHS(═O)₂CH₃ and —N(CH₃)S(═O)₂C₆H₅. Sulfinamino: —NR¹S(═O)R, wherein R¹ is an amino substituent, as defined for amino groups, and R is a sulfinamino substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfinamino groups include, but are not limited to, —NHS(═O)CH₃ and —N(CH₃)S(═O)C₆H₅. Phosphino (phosphine): —PR₂, wherein R is a phosphino substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphino groups include, but are not limited to, —PH₂, —P(CH₃)₂, —P(CH₂CH₃)₂, —P(t-Bu)₂, and —P(Ph)₂. Phospho: —P(═O)₂. Phosphinyl (phosphine oxide): —P(═O)R₂, wherein R is a phosphinyl substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group or a C₅₋₂₀ aryl group. Examples of phosphinyl groups include, but are not limited to, —P(═O)(CH₃)₂, —P(═O)(CH₂CH₃)₂, —P(═O)(t-Bu)₂, and —P(═O)(Ph)₂. Phosphonic acid (phosphono): —P(═O)(OH)₂. Phosphonate (phosphono ester): —P(═O)(OR)₂, where R is a phosphonate substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphonate groups include, but are not limited to, —P(═O)(OCH₃)₂, —P(═O)(OCH₂CH₃)₂, —P(═O)(O-t-Bu)₂, and —P(═O)(OPh)₂. Phosphoric acid (phosphonooxy): —OP(═O)(OH)₂. Phosphate (phosphonooxy ester): —OP(═O)(OR)₂, where R is a phosphate substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphate groups include, but are not limited to, —OP(═O)(OCH₃)₂, —OP(═O)(OCH₂CH₃)₂, —OP(═O)(O-t-Bu)₂, and —OP(═O)(OPh)₂. Phosphorous acid: —OP(OH)₂. Phosphite: —OP(OR)₂, where R is a phosphite substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphite groups include, but are not limited to, —OP(OCH₃)₂, —OP(OCH₂CH₃)₂, —OP(O-t-Bu)₂, and —OP(OPh)₂. Phosphoramidite: —OP(OR¹)—NR² ₂, where R¹ and R² are phosphoramidite substituents, for example, —H, a (optionally substituted) C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphoramidite groups include, but are not limited to, —OP(OCH₂CH₃)—N(CH₃)₂, —OP(OCH₂CH₃)—N(i-Pr)₂, and —OP(OCH₂CH₂CN)—N(i-Pr)₂. Phosphoramidate: —OP(═O)(OR¹)—NR² ₂, where R¹ and R² are phosphoramidate substituents, for example, —H, a (optionally substituted) C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphoramidate groups include, but are not limited to, —OP(═O)(OCH₂CH₃)—N(CH₃)₂, —OP(═O)(OCH₂CH₃)—N(i-Pr)₂, and —OP(═O)(OCH₂CH₂CN)—N(i-Pr)₂. Alkylene C₃₋₁₂ alkylene: The term “C₃₋₁₂ alkylene”, as used herein, pertains to a bidentate moiety obtained by removing two hydrogen atoms, either both from the same carbon atom, or one from each of two different carbon atoms, of a hydrocarbon compound having from 3 to 12 carbon atoms (unless otherwise specified), which may be aliphatic or alicyclic, and which may be saturated, partially unsaturated, or fully unsaturated. Thus, the term “alkylene” includes the sub-classes alkenylene, alkynylene, cycloalkylene, etc., discussed below.

Examples of linear saturated C₃₋₁₂ alkylene groups include, but are not limited to, —(CH₂)_(n)— where n is an integer from 3 to 12, for example, —CH₂CH₂CH₂— (propylene), —CH₂CH₂CH₂CH₂— (butylene), —CH₂CH₂CH₂CH₂CH₂— (pentylene) and —CH₂CH₂CH₂CH-₂CH₂CH₂CH₂— (heptylene).

Examples of branched saturated C₃₋₁₂ alkylene groups include, but are not limited to, —CH(CH₃)CH₂—, —CH(CH₃)CH₂CH₂—, —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂—, —CH₂CH(CH₃)CH₂CH₂—, —CH(CH₂CH₃)—, —CH(CH₂CH₃)CH₂—, and —CH₂CH(CH₂CH₃)CH₂—.

Examples of linear partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ alkenylene, and alkynylene groups) include, but are not limited to, —CH═CH—CH₂—, —CH₂—CH═CH₂—, —CH═CH—CH₂—CH₂—, —CH═CH—CH₂—CH₂—CH₂—, —CH═CH—CH═CH—, —CH═CH—CH═CH—CH₂—, —CH═CH—CH═CH—CH₂—CH₂—, —CH═CH—CH₂—CH═CH—, —CH═CH—CH₂—CH₂—CH═CH—, and —CH₂—C≡C—CH₂—.

Examples of branched partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ alkenylene and alkynylene groups) include, but are not limited to, —C(CH₃)═CH—, —C(CH₃)═CH—CH₂—, —CH═CH—CH(CH₃)— and —C≡C—CH(CH₃)—.

Examples of alicyclic saturated C₃₋₁₂ alkylene groups (C₃₋₁₂ cycloalkylenes) include, but are not limited to, cyclopentylene (e.g. cyclopent-1,3-ylene), and cyclohexylene (e.g. cyclohex-1,4-ylene).

Examples of alicyclic partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ cycloalkylenes) include, but are not limited to, cyclopentenylene (e.g. 4-cyclopenten-1,3-ylene), cyclohexenylene (e.g. 2-cyclohexen-1,4-ylene; 3-cyclohexen-1,2-ylene; 2,5-cyclohexadien-1,4-ylene).

Carbamate nitrogen protecting group: the term “carbamate nitrogen protecting group” pertains to a moiety which masks the nitrogen in the imine bond, and these are well known in the art. These groups have the following structure:

wherein R′¹⁰ is R as defined above. A large number of suitable groups are described on pages 503 to 549 of Greene, T. W. and Wuts, G. M., Protective Groups in Organic Synthesis, 3^(rd) Edition, John Wiley & Sons, Inc., 1999, which is incorporated herein by reference.

Hemi-aminal nitrogen protecting group: the term “hemi-aminal nitrogen protecting group” pertains to a group having the following structure:

wherein R′¹⁰ is R as defined above. A large number of suitable groups are described on pages 633 to 647 as amide protecting groups of Greene, T. W. and Wuts, G. M., Protective Groups in Organic Synthesis, 3^(rd) Edition, John Wiley & Sons, Inc., 1999, which is incorporated herein by reference.

The groups Carbamate nitrogen protecting group and Hemi-aminal nitrogen protecting group may be jointly termed a “nitrogen protecting group for synthesis”.

Conjugates

The present invention provides a conjugate comprising a PBD compound connected to the antibody via a Linker Unit.

In one embodiment, the conjugate comprises the antibody connected to a spacer connecting group, the spacer connected to a trigger, the trigger connected to a self-immolative linker, and the self-immolative linker connected to the N10 position of the PBD compound. Such a conjugate is illustrated below:

where Ab is the antibody as defined above and PBD is a pyrrolobenzodiazepine compound (D), as described herein. The illustration shows the portions that correspond to R^(L′), A, L¹ and L² in certain embodiments of the invention. R^(L′) may be either R^(L1′) or R^(L2′). D is D^(L) with R^(L1′) or R^(L2′) removed.

The present invention is suitable for use in providing a PBD compound to a preferred site in a subject. In the preferred embodiments, the conjugate allows the release of an active PBD compound that does not retain any part of the linker. There is no stub present that could affect the reactivity of the PBD compound.

The linker attaches the antibody to the PBD drug moiety D through covalent bond(s). The linker is a bifunctional or multifunctional moiety which can be used to link one or more drug moiety (D) and an antibody unit (Ab) to form antibody-drug conjugates (ADC). The linker (R^(L′)) may be stable outside a cell, i.e. extracellular, or it may be cleavable by enzymatic activity, hydrolysis, or other metabolic conditions. Antibody-drug conjugates (ADC) can be conveniently prepared using a linker having reactive functionality for binding to the drug moiety and to the antibody. A cysteine thiol, or an amine, e.g. N-terminus or amino acid side chain such as lysine, of the antibody (Ab) can form a bond with a functional group of a linker or spacer reagent, PBD drug moiety (D) or drug-linker reagent (D^(L), D-R^(L)), where R^(L) can be R^(L1) or R^(L2).

The linkers of the ADC preferably prevent aggregation of ADC molecules and keep the ADC freely soluble in aqueous media and in a monomeric state.

The linkers of the ADC are preferably stable extracellularly. Before transport or delivery into a cell, the antibody-drug conjugate (ADC) is preferably stable and remains intact, i.e. the antibody remains linked to the drug moiety. The linkers are stable outside the target cell and may be cleaved at some efficacious rate inside the cell. An effective linker will: (i) maintain the specific binding properties of the antibody; (ii) allow intracellular delivery of the conjugate or drug moiety; (iii) remain stable and intact, i.e. not cleaved, until the conjugate has been delivered or transported to its targeted site; and (iv) maintain a cytotoxic, cell-killing effect or a cytostatic effect of the PBD drug moiety. Stability of the ADC may be measured by standard analytical techniques such as mass spectroscopy, HPLC, and the separation/analysis technique LC/MS.

Covalent attachment of the antibody and the drug moiety requires the linker to have two reactive functional groups, i.e. bivalency in a reactive sense. Bivalent linker reagents which are useful to attach two or more functional or biologically active moieties, such as peptides, nucleic acids, drugs, toxins, antibodies, haptens, and reporter groups are known, and methods have been described their resulting conjugates (Hermanson, G. T. (1996) Bioconjugate Techniques; Academic Press: New York, p 234-242).

In another embodiment, the linker may be substituted with groups which modulate aggregation, solubility or reactivity. For example, a sulfonate substituent may increase water solubility of the reagent and facilitate the coupling reaction of the linker reagent with the antibody or the drug moiety, or facilitate the coupling reaction of Ab-L with D^(L), or D^(L)-L with Ab, depending on the synthetic route employed to prepare the ADC.

In one embodiment, L-R^(L′) is a group:

-   -   where the asterisk indicates the point of attachment to the Drug         Unit (D), Ab is the antibody (L), L¹ is a linker, A is a         connecting group connecting L¹ to the antibody, L² is a covalent         bond or together with —OC(═O)— forms a self-immolative linker,         and L¹ or L² is a cleavable linker.

L¹ is preferably the cleavable linker, and may be referred to as a trigger for activation of the linker for cleavage.

The nature of L¹ and L², where present, can vary widely. These groups are chosen on the basis of their cleavage characteristics, which may be dictated by the conditions at the site to which the conjugate is delivered. Those linkers that are cleaved by the action of enzymes are preferred, although linkers that are cleavable by changes in pH (e.g. acid or base labile), temperature or upon irradiation (e.g. photolabile) may also be used. Linkers that are cleavable under reducing or oxidising conditions may also find use in the present invention.

L¹ may comprise a contiguous sequence of amino acids. The amino acid sequence may be the target substrate for enzymatic cleavage, thereby allowing release of L-R^(L′) from the N10 position.

In one embodiment, L¹ is cleavable by the action of an enzyme. In one embodiment, the enzyme is an esterase or a peptidase.

In one embodiment, L² is present and together with —C(═O)O— forms a self-immolative linker.

In one embodiment, L² is a substrate for enzymatic activity, thereby allowing release of L-R^(L′) from the N10 position.

In one embodiment, where L¹ is cleavable by the action of an enzyme and L² is present, the enzyme cleaves the bond between L¹ and L².

L¹ and L², where present, may be connected by a bond selected from:

-   -   —C(═O)NH—,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)NH—, and     -   —NHC(═O)NH—.

An amino group of L¹ that connects to L² may be the N-terminus of an amino acid or may be derived from an amino group of an amino acid side chain, for example a lysine amino acid side chain.

A carboxyl group of L¹ that connects to L² may be the C-terminus of an amino acid or may be derived from a carboxyl group of an amino acid side chain, for example a glutamic acid amino acid side chain.

A hydroxyl group of L¹ that connects to L² may be derived from a hydroxyl group of an amino acid side chain, for example a serine amino acid side chain.

The term “amino acid side chain” includes those groups found in: (i) naturally occurring amino acids such as alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine; (ii) minor amino acids such as ornithine and citrulline; (iii) unnatural amino acids, beta-amino acids, synthetic analogs and derivatives of naturally occurring amino acids; and (iv) all enantiomers, diastereomers, isomerically enriched, isotopically labelled (e.g. ²H, ³H, ¹⁴C, ¹⁵N), protected forms, and racemic mixtures thereof.

In one embodiment, —C(═O)O— and L² together form the group:

-   -   where the asterisk indicates the point of attachment to the N10         position, the wavy line indicates the point of attachment to the         linker L¹, Y is —N(H)—, —O—, —C(═O)N(H)— or —C(═O)O—, and n is 0         to 3. The phenylene ring is optionally substituted with one, two         or three substituents as described herein. In one embodiment,         the phenylene group is optionally substituted with halo, NO₂, R         or OR.

In one embodiment, Y is NH.

In one embodiment, n is 0 or 1. Preferably, n is 0.

Where Y is NH and n is 0, the self-immolative linker may be referred to as a p-aminobenzylcarbonyl linker (PABC).

The self-immolative linker will allow for release of the protected compound when a remote site is activated, proceeding along the lines shown below (for n=0):

-   -   where L* is the activated form of the remaining portion of the         linker. These groups have the advantage of separating the site         of activation from the compound being protected. As described         above, the phenylene group may be optionally substituted.

In one embodiment described herein, the group L* is a linker L¹ as described herein, which may include a dipeptide group.

In another embodiment, —C(═O)O— and L² together form a group selected from:

-   -   where the asterisk, the wavy line, Y, and n are as defined         above. Each phenylene ring is optionally substituted with one,         two or three substituents as described herein. In one         embodiment, the phenylene ring having the Y substituent is         optionally substituted and the phenylene ring not having the Y         substituent is unsubstituted. In one embodiment, the phenylene         ring having the Y substituent is unsubstituted and the phenylene         ring not having the Y substituent is optionally substituted.

In another embodiment, —C(═O)O— and L² together form a group selected from:

-   -   where the asterisk, the wavy line, Y, and n are as defined         above, E is O, S or NR, D is N, CH, or CR, and F is N, CH, or         CR.

In one embodiment, D is N.

In one embodiment, D is CH.

In one embodiment, E is O or S.

In one embodiment, F is CH.

In a preferred embodiment, the linker is a cathepsin labile linker.

In one embodiment, L¹ comprises a dipeptide The dipeptide may be represented as —NH—X₁—X₂—CO—, where —NH— and —CO— represent the N- and C-terminals of the amino acid groups X₁ and X₂ respectively. The amino acids in the dipeptide may be any combination of natural amino acids. Where the linker is a cathepsin labile linker, the dipeptide may be the site of action for cathepsin-mediated cleavage.

Additionally, for those amino acids groups having carboxyl or amino side chain functionality, for example Glu and Lys respectively, CO and NH may represent that side chain functionality.

In one embodiment, the group —X₁—X₂— in dipeptide, —NH—X₁—X₂—CO—, is selected from:

-   -   -Phe-Lys-,     -   -Val-Ala-,     -   -Val-Lys-,     -   -Ala-Lys-,     -   -Val-Cit-,     -   -Phe-Cit-,     -   -Leu-Cit-,     -   -Ile-Cit-,     -   -Phe-Arg-,     -   -Trp-Cit-         where Cit is citrulline.

Preferably, the group —X₁—X₂— in dipeptide, —NH—X₁—X₂—CO—, is selected from:

-   -   -Phe-Lys-,     -   -Val-Ala-,     -   -Val-Lys-,     -   -Ala-Lys-,     -   -Val-Cit-.

Most preferably, the group —X₁—X₂— in dipeptide, —NH—X, —X₂—CO—, is -Phe-Lys- or -Val-Ala-.

Other dipeptide combinations may be used, including those described by Dubowchik et al., Bioconjugate Chemistry, 2002, 13, 855-869, which is incorporated herein by reference.

In one embodiment, the amino acid side chain is derivatised, where appropriate. For example, an amino group or carboxy group of an amino acid side chain may be derivatised.

In one embodiment, an amino group NH₂ of a side chain amino acid, such as lysine, is a derivatised form selected from the group consisting of NHR and NRR′.

In one embodiment, a carboxy group COOH of a side chain amino acid, such as aspartic acid, is a derivatised form selected from the group consisting of COOR, CONH₂, CONHR and CONRR′.

In one embodiment, the amino acid side chain is chemically protected, where appropriate. The side chain protecting group may be a group as discussed below in relation to the group R^(L). The present inventors have established that protected amino acid sequences are cleavable by enzymes. For example, it has been established that a dipeptide sequence comprising a Boc side chain-protected Lys residue is cleavable by cathepsin.

Protecting groups for the side chains of amino acids are well known in the art and are described in the Novabiochem Catalog. Additional protecting group strategies are set out in Protective Groups in Organic Synthesis, Greene and Wuts.

Possible side chain protecting groups are shown below for those amino acids having reactive side chain functionality:

-   -   Arg: Z, Mtr, Tos;     -   Asn: Trt, Xan;     -   Asp: Bzl, t-Bu;     -   Cys: Acm, Bzl, Bzl-OMe, Bzl-Me, Trt;     -   Glu: Bzl, t-Bu;     -   Gin: Trt, Xan;     -   His: Boc, Dnp, Tos, Trt;     -   Lys: Boc, Z—Cl, Fmoc, Z, Alloc;     -   Ser: Bzl, TBDMS, TBDPS;     -   Thr: Bz;     -   Trp: Boc;     -   Tyr: Bzl, Z, Z—Br.

In one embodiment, the side chain protection is selected to be orthogonal to a group provided as, or as part of, a capping group, where present. Thus, the removal of the side chain protecting group does not remove the capping group, or any protecting group functionality that is part of the capping group.

In other embodiments of the invention, the amino acids selected are those having no reactive side chain functionality. For example, the amino acids may be selected from: Ala, Gly, Ile, Leu, Met, Phe, Pro, and Val.

In one embodiment, the dipeptide is used in combination with a self-immolative linker. The self-immolative linker may be connected to —X₂—.

Where a self-immolative linker is present, —X₂— is connected directly to the self-immolative linker. Preferably the group —X₂—CO— is connected to Y, where Y is NH, thereby forming the group —X₂—CO—NH—.

—NH—X₁— is connected directly to A. A may comprise the functionality —CO— thereby to form an amide link with —X₁—.

In one embodiment, L¹ and L² together with —OC(═O)— comprise the group NH—X₁—X₂—CO-PABC-. The PABC group is connected directly to the N10 position.

Preferably, the self-immolative linker and the dipeptide together form the group —NH-Phe-Lys-CO—NH-PABC-, which is illustrated below:

-   -   where the asterisk indicates the point of attachment to the N10         position, and the wavy line indicates the point of attachment to         the remaining portion of the linker L¹ or the point of         attachment to A. Preferably, the wavy line indicates the point         of attachment to A. The side chain of the Lys amino acid may be         protected, for example, with Boc, Fmoc, or Alloc, as described         above.

Alternatively, the self-immolative linker and the dipeptide together form the group —NH-Val-Ala-CO—NH-PABC-, which is illustrated below:

-   -   where the asterisk and the wavy line are as defined above.

Alternatively, the self-immolative linker and the dipeptide together form the group —NH-Val-Cit-CO—NH-PABC-, which is illustrated below:

-   -   where the asterisk and the wavy line are as defined above.

In one embodiment, A is a covalent bond. Thus, L¹ and the antibody are directly connected. For example, where L¹ comprises a contiguous amino acid sequence, the N-terminus of the sequence may connect directly to the antibody.

Thus, where A is a covalent bond, the connection between the antibody and L¹ may be selected from:

-   -   —C(═O)NH—,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)NH—,     -   —NHC(═O)NH—,     -   —C(═O)NHC(═O)—,     -   —S—,     -   —S—S—,     -   —CH₂C(═O)—, and     -   ═N—NH—.

An amino group of L¹ that connects to the antibody may be the N-terminus of an amino acid or may be derived from an amino group of an amino acid side chain, for example a lysine amino acid side chain.

An carboxyl group of L¹ that connects to the antibody may be the C-terminus of an amino acid or may be derived from a carboxyl group of an amino acid side chain, for example a glutamic acid amino acid side chain.

A hydroxyl group of L¹ that connects to the antibody may be derived from a hydroxyl group of an amino acid side chain, for example a serine amino acid side chain.

A thiol group of L¹ that connects to the antibody may be derived from a thiol group of an amino acid side chain, for example a serine amino acid side chain.

The comments above in relation to the amino, carboxyl, hydroxyl and thiol groups of L¹ also apply to the antibody.

In one embodiment, L² together with —OC(═O)— represents:

-   -   where the asterisk indicates the point of attachment to the N10         position, the wavy line indicates the point of attachment to L¹,         n is 0 to 3, Y is a covalent bond or a functional group, and E         is an activatable group, for example by enzymatic action or         light, thereby to generate a self-immolative unit. The phenylene         ring is optionally further substituted with one, two or three         substituents as described herein. In one embodiment, the         phenylene group is optionally further substituted with halo,         NO₂, R or OR. Preferably n is 0 or 1, most preferably 0.

E is selected such that the group is susceptible to activation, e.g. by light or by the action of an enzyme. E may be —NO₂ or glucoronic acid. The former may be susceptible to the action of a nitroreductase, the latter to the action of a β-glucoronidase.

In this embodiment, the self-immolative linker will allow for release of the protected compound when E is activated, proceeding along the lines shown below (for n=0):

-   -   where the asterisk indicates the point of attachment to the N10         position, E is the activated form of E, and Y is as described         above. These groups have the advantage of separating the site of         activation from the compound being protected. As described         above, the phenylene group may be optionally further         substituted.

The group Y may be a covalent bond to L¹.

The group Y may be a functional group selected from:

-   -   —C(═O)—     -   —NH—     -   —O—     -   —C(═O)NH—,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)NH—,     -   —NHC(═O)NH—,     -   —NHC(═O)NH,     -   —C(═O)NHC(═O)—, and     -   —S—.

Where L¹ is a dipeptide, it is preferred that Y is —NH— or —C(═O)—, thereby to form an amide bond between L¹ and Y. In this embodiment, the dipeptide sequence need not be a substrate for an enzymatic activity.

In another embodiment, A is a spacer group. Thus, L¹ and the antibody are indirectly connected.

L¹ and A may be connected by a bond selected from:

-   -   —C(═O)NH—,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)NH—, and     -   —NHC(═O)NH—.

In one embodiment, the group A is:

-   -   where the asterisk indicates the point of attachment to L¹, the         wavy line indicates the point of attachment to the antibody, and         n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the group A is:

-   -   where the asterisk indicates the point of attachment to L¹, the         wavy line indicates the point of attachment to the antibody, and         n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the group A is:

-   -   where the asterisk indicates the point of attachment to L¹, the         wavy line indicates the point of attachment to the antibody, n         is 0 or 1, and m is 0 to 30. In a preferred embodiment, n is 1         and m is 0 to 10, 1 to 8, preferably 4 to 8, and most preferably         4 or 8. In another embodiment, m is 10 to 30, and preferably 20         to 30. Alternatively, m is 0 to 50. In this embodiment, m is         preferably 10-40 and n is 1.

In one embodiment, the group A is:

-   -   where the asterisk indicates the point of attachment to L¹ the         wavy line indicates the point of attachment to the antibody, n         is 0 or 1, and m is 0 to 30. In a preferred embodiment, n is 1         and m is 0 to 10, 1 to 8, preferably 4 to 8, and most preferably         4 or 8. In another embodiment, m is 10 to 30, and preferably 20         to 30. Alternatively, m is 0 to 50. In this embodiment, m is         preferably 10-40 and n is 1.

In one embodiment, the connection between the antibody and A is through a thiol residue of the antibody and a maleimide group of A.

In one embodiment, the connection between the antibody and A is:

-   -   where the asterisk indicates the point of attachment to the         remaining portion of A and the wavy line indicates the point of         attachment to the remaining portion of the antibody. In this         embodiment, the S atom is typically derived from the antibody.

In each of the embodiments above, an alternative functionality may be used in place of the maleimide-derived group shown below:

-   -   where the wavy line indicates the point of attachment to the         antibody as before, and the asterisk indicates the bond to the         remaining portion of the A group.

In one embodiment, the maleimide-derived group is replaced with the group:

-   -   where the wavy line indicates point of attachment to the         antibody, and the asterisk indicates the bond to the remaining         portion of the A group.

In one embodiment, the maleimide-derived group is replaced with a group, which optionally together with the antibody, is selected from:

-   -   —C(═O)NH—,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)NH—,     -   —NHC(═O)NH—,     -   —NHC(═O)NH,     -   —C(═O)NHC(═O)—,     -   —S—,     -   —S—S—,     -   —CH₂C(═O)—     -   —C(═O)CH₂—,     -   ═N—NH—, and     -   —NH—N═.

In one embodiment, the maleimide-derived group is replaced with a group, which optionally together with the antibody, is selected from:

-   -   where the wavy line indicates either the point of attachment to         the antibody or the bond to the remaining portion of the A         group, and the asterisk indicates the other of the point of         attachment to the antibody or the bond to the remaining portion         of the A group.

Other groups suitable for connecting L¹ to the antibody are described in WO 2005/082023.

In one embodiment, the Connecting Group A is present, the Trigger L¹ is present and Self-Immolative Linker L² is absent. Thus, L¹ and the Drug unit are directly connected via a bond. Equivalently in this embodiment, L² is a bond. This may be particularly relevant when D^(L) is of Formula II.

L¹ and D may be connected by a bond selected from:

-   -   —C(═O)N<,     -   —C(═O)O—,     -   —NHC(═O)—,     -   —OC(═O)—,     -   —OC(═O)O—,     -   —NHC(═O)O—,     -   —OC(═O)N<, and     -   —NHC(═O)N<,         where N< or O— are part of D.

In one embodiment, L¹ and D are preferably connected by a bond selected from:

-   -   —C(═O)N<, and     -   —NHC(═O)—.

In one embodiment, L¹ comprises a dipeptide and one end of the dipeptide is linked to D. As described above, the amino acids in the dipeptide may be any combination of natural amino acids and non-natural amino acids. In some embodiments, the dipeptide comprises natural amino acids. Where the linker is a cathepsin labile linker, the dipeptide is the site of action for cathepsin-mediated cleavage. The dipeptide then is a recognition site for cathepsin.

In one embodiment, the group —X₁—X₂— in dipeptide, —NH—X₁—X₂—CO—, is selected from:

-   -   -Phe-Lys-,     -   -Val-Ala-,     -   -Val-Lys-,     -   -Ala-Lys-,     -   -Val-Cit-,     -   -Phe-Cit-,     -   -Leu-Cit-,     -   -Ile-Cit-,     -   -Phe-Arg-, and     -   -Trp-Cit-;         where Cit is citrulline. In such a dipeptide, —NH— is the amino         group of X₁, and CO is the carbonyl group of X₂.

Preferably, the group —X₁—X₂— in dipeptide, —NH—X₁—X₂—CO—, is selected from:

-   -   -Phe-Lys-,     -   -Val-Ala-,     -   -Val-Lys-,     -   -Ala-Lys-, and     -   -Val-Cit-.

Most preferably, the group —X₁—X₂— in dipeptide, —NH—X, —X₂—CO—, is -Phe-Lys- or -Val-Ala-.

Other dipeptide combinations of interest include:

-   -   -Gly-Gly-,     -   -Pro-Pro-, and     -   -Val-Glu-.

Other dipeptide combinations may be used, including those described above.

In one embodiment, L¹-D is:

-NH—X₁—X₂—CO—N<*

-   -   where —NH—X₁—X₂—CO is the dipeptide, —N< is part of the Drug         unit, the asterisk indicates the points of attachment to the         remainder of the Drug unit, and the wavy line indicates the         point of attachment to the remaining portion of L¹ or the point         of attachment to A. Preferably, the wavy line indicates the         point of attachment to A.

In one embodiment, the dipeptide is valine-alanine and L¹-D is:

-   -   where the asterisks, —N< and the wavy line are as defined above.

In one embodiment, the dipeptide is phenylalnine-lysine and L¹-D is:

-   -   where the asterisks, —N< and the wavy line are as defined above.

In one embodiment, the dipeptide is valine-citrulline.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, n is 0 or 1, and m is 0 to 30. In a preferred embodiment,         n is 1 and m is 0 to 10, 1 to 8, preferably 4 to 8, most         preferably 4 or 8.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, n is 0 or 1, and m is 0 to 30. In a preferred embodiment,         n is 1 and m is 0 to 10, 1 to 7, preferably 3 to 7, most         preferably 3 or 7.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, n is 0 or 1, and m is 0 to 30. In a preferred embodiment,         n is 1 and m is 0 to 10, 1 to 8, preferably 4 to 8, most         preferably 4 or 8.

In one embodiment, the groups A-L¹ is:

-   -   where the asterisk indicates the point of attachment to L or D,         the wavy line indicates the point of attachment to the Ligand         unit, n is 0 or 1, and m is 0 to 30. In a preferred embodiment,         n is 1 and m is 0 to 10, 1 to 8, preferably 4 to 8, most         preferably 4 or 8.

In one embodiment, the groups A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         S is a sulfur group of the Ligand unit, the wavy line indicates         the point of attachment to the rest of the Ligand unit, and n is         0 to 6. In one embodiment, n is 5.

In one embodiment, the group A-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         S is a sulfur group of the Ligand unit, the wavy line indicates         the point of attachment to the remainder of the Ligand unit, and         n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         S is a sulfur group of the Ligand unit, the wavy line indicates         the point of attachment to the remainder of the Ligand unit, n         is 0 or 1, and m is 0 to 30. In a preferred embodiment, n is 1         and m is 0 to 10, 1 to 8, preferably 4 to 8, most preferably 4         or 8.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the Ligand         unit, n is 0 or 1, and m is 0 to 30. In a preferred embodiment,         n is 1 and m is 0 to 10, 1 to 7, preferably 4 to 8, most         preferably 4 or 8.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the remainder         of the Ligand unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the remainder         of the Ligand unit, and n is 0 to 6. In one embodiment, n is 5.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the remainder         of the Ligand unit, n is 0 or 1, and m is 0 to 30. In a         preferred embodiment, n is 1 and m is 0 to 10, 1 to 8,         preferably 4 to 8, most preferably 4 or 8.

In one embodiment, the groups A¹-L¹ are:

-   -   where the asterisk indicates the point of attachment to L² or D,         the wavy line indicates the point of attachment to the remainder         of the Ligand unit, n is 0 or 1, and m is 0 to 30. In a         preferred embodiment, n is 1 and m is 0 to 10, 1 to 8,         preferably 4 to 8, most preferably 4 or 8.

The group R^(L′) is derivable from the group R^(L). The group R^(L) may be converted to a group R^(L′) by connection of an antibody to a functional group of R^(L). Other steps may be taken to convert R^(L) to R^(L′). These steps may include the removal of protecting groups, where present, or the installation of an appropriate functional group.

R^(L)

Linkers can include protease-cleavable peptidic moieties comprising one or more amino acid units. Peptide linker reagents may be prepared by solid phase or liquid phase synthesis methods (E. Schröder and K. Lübke, The Peptides, volume 1, pp 76-136 (1965) Academic Press) that are well known in the field of peptide chemistry, including t-BOC chemistry (Geiser et al “Automation of solid-phase peptide synthesis” in Macromolecular Sequencing and Synthesis, Alan R. Liss, Inc., 1988, pp. 199-218) and Fmoc/HBTU chemistry (Fields, G. and Noble, R. (1990) “Solid phase peptide synthesis utilizing 9-fluoroenylmethoxycarbonyl amino acids”, Int. J. Peptide Protein Res. 35:161-214), on an automated synthesizer such as the Rainin Symphony Peptide Synthesizer (Protein Technologies, Inc., Tucson, Ariz.), or Model 433 (Applied Biosystems, Foster City, Calif.).

Exemplary amino acid linkers include a dipeptide, a tripeptide, a tetrapeptide or a pentapeptide. Exemplary dipeptides include: valine-citrulline (vc or val-cit), alanine-phenylalanine (af or ala-phe). Exemplary tripeptides include: glycine-valine-citrulline (gly-val-cit) and glycine-glycine-glycine (gly-gly-gly). Amino acid residues which comprise an amino acid linker component include those occurring naturally, as well as minor amino acids and non-naturally occurring amino acid analogs, such as citrulline. Amino acid linker components can be designed and optimized in their selectivity for enzymatic cleavage by a particular enzymes, for example, a tumor-associated protease, cathepsin B, C and D, or a plasmin protease.

Amino acid side chains include those occurring naturally, as well as minor amino acids and non-naturally occurring amino acid analogs, such as citrulline. Amino acid side chains include hydrogen, methyl, isopropyl, isobutyl, sec-butyl, benzyl, p-hydroxybenzyl, —CH₂OH, —CH(OH)CH₃, —CH₂CH₂SCH₃, —CH₂CONH₂, —CH₂COOH, —CH₂CH₂CONH₂, —CH₂CH₂COOH, —(CH₂)₃NHC(═NH)NH₂, —(CH₂)₃NH₂, —(CH₂)₃NHCOCH₃, —(CH₂)₃NHCHO, —(CH₂)₄NHC(═NH)NH₂, —(CH₂)₄NH₂, —(CH₂)₄NHCOCH₃, —(CH₂)₄NHCHO, —(CH₂)₃NHCONH₂, —(CH₂)₄NHCONH₂, —CH₂CH₂CH(OH)CH₂NH₂, 2-pyridylmethyl-, 3-pyridylmethyl-, 4-pyridylmethyl-, phenyl, cyclohexyl, as well as the following structures:

When the amino acid side chains include other than hydrogen (glycine), the carbon atom to which the amino acid side chain is attached is chiral. Each carbon atom to which the amino acid side chain is attached is independently in the (S) or (R) configuration, or a racemic mixture. Drug-linker reagents may thus be enantiomerically pure, racemic, or diastereomeric.

In exemplary embodiments, amino acid side chains are selected from those of natural and non-natural amino acids, including alanine, 2-amino-2-cyclohexylacetic acid, 2-amino-2-phenylacetic acid, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, norleucine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, γ-aminobutyric acid, α,α-dimethyl γ-aminobutyric acid, β,β-dimethyl γ-aminobutyric acid, ornithine, and citrulline (Cit).

An exemplary valine-citrulline (val-cit or vc) dipeptide linker reagent useful for constructing a linker-PBD drug moiety intermediate for conjugation to an antibody, having a para-aminobenzylcarbamoyl (PAB) self-immolative spacer has the structure:

where Q is C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -halogen, —NO₂ or —CN; and m is an integer ranging from 0-4.

An exemplary phe-lys(Mtr) dipeptide linker reagent having a p-aminobenzyl group can be prepared according to Dubowchik, et al. (1997) Tetrahedron Letters, 38:5257-60, and has the structure:

where Mtr is mono-4-methoxytrityl, Q is C₁-C₈ alkyl, —O—(C₁-C₈ alkyl), -halogen, —NO₂ or —CN; and m is an integer ranging from 0-4.

The “self-immolative linker” PAB (para-aminobenzyloxycarbonyl), attaches the drug moiety to the antibody in the antibody drug conjugate (Carl et al (1981) J. Med. Chem. 24:479-480; Chakravarty et al (1983) J. Med. Chem. 26:638-644; U.S. Pat. No. 6,214,345; US20030130189; US20030096743; U.S. Pat. No. 6,759,509; US20040052793; U.S. Pat. Nos. 6,218,519; 6,835,807; 6,268,488; US20040018194; WO98/13059; US20040052793; U.S. Pat. Nos. 6,677,435; 5,621,002; US20040121940; WO2004/032828). Other examples of self-immolative spacers besides PAB include, but are not limited to: (i) aromatic compounds that are electronically similar to the PAB group such as 2-aminoimidazol-5-methanol derivatives (Hay et al. (1999) Bioorg. Med. Chem. Lett. 9:2237), thiazoles (U.S. Pat. No. 7,375,078), multiple, elongated PAB units (de Groot et al (2001) J. Org. Chem. 66:8815-8830); and ortho or para-aminobenzylacetals; and (ii) homologated styryl PAB analogs (U.S. Pat. No. 7,223,837). Spacers can be used that undergo cyclization upon amide bond hydrolysis, such as substituted and unsubstituted 4-aminobutyric acid amides (Rodrigues et al (1995) Chemistry Biology 2:223), appropriately substituted bicyclo[2.2.1] and bicyclo[2.2.2] ring systems (Storm et al (1972) J. Amer. Chem. Soc. 94:5815) and 2-aminophenylpropionic acid amides (Amsberry, et al (1990) J. Org. Chem. 55:5867). Elimination of amine-containing drugs that are substituted at glycine (Kingsbury et al (1984) J. Med. Chem. 27:1447) are also examples of self-immolative spacers useful in ADC.

In one embodiment, a valine-citrulline dipeptide PAB analog reagent has a 2,6 dimethyl phenyl group and has the structure:

Linker reagents useful for the antibody drug conjugates of the invention include, but are not limited to: BMPEO, BMPS, EMCS, GMBS, HBVS, LC-SMCC, MBS, MPBH, SBAP, SIA, SIAB, SMCC, SMPB, SMPH, sulfo-EMCS, sulfo-GMBS, sulfo-KMUS, sulfo-MBS, sulfo-SIAB, sulfo-SMCC, and sulfo-SMPB, and SVSB (succinimidyl-(4-vinylsulfone)benzoate), and bis-maleimide reagents: DTME, BMB, BMDB, BMH, BMOE, 1,8-bis-maleimidodiethyleneglycol (BM(PEO)₂), and 1,11-bis-maleimidotriethyleneglycol (BM(PEO)₃), which are commercially available from Pierce Biotechnology, Inc., ThermoScientific, Rockford, Ill., and other reagent suppliers. Bis-maleimide reagents allow the attachment of a free thiol group of a cysteine residue of an antibody to a thiol-containing drug moiety, label, or linker intermediate, in a sequential or concurrent fashion. Other functional groups besides maleimide, which are reactive with a thiol group of an antibody, PBD drug moiety, or linker intermediate include iodoacetamide, bromoacetamide, vinyl pyridine, disulfide, pyridyl disulfide, isocyanate, and isothiocyanate.

Other embodiments of linker reagents are: N-succinimidyl-4-(2-pyridylthio)pentanoate (SPP), N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP, Carlsson et al (1978) Biochem. J. 173:723-737), succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), iminothiolane (IT), bifunctional derivatives of imidoesters (such as dimethyl adipimidate HCl), active esters (such as disuccinimidyl suberate), aldehydes (such as glutaraldehyde), bis-azido compounds (such as bis(p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such as bis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such as toluene 2,6-diisocyanate), and bis-active fluorine compounds (such as 1,5-difluoro-2,4-dinitrobenzene). Useful linker reagents can also be obtained via other commercial sources, such as Molecular Biosciences Inc. (Boulder, Colo.), or synthesized in accordance with procedures described in Toki et al (2002) J. Org. Chem. 67:1866-1872; U.S. Pat. No. 6,214,345; WO 02/088172; US 2003130189; US2003096743; WO 03/026577; WO 03/043583; and WO 04/032828.

The Linker may be a dendritic type linker for covalent attachment of more than one drug moiety through a branching, multifunctional linker moiety to an antibody (US 2006/116422; US 2005/271615; de Groot et al (2003) Angew. Chem. Int. Ed. 42:4490-4494; Amir et al (2003) Angew. Chem. Int. Ed. 42:4494-4499; Shamis et al (2004) J. Am. Chem. Soc. 126:1726-1731; Sun et al (2002) Bioorganic & Medicinal Chemistry Letters 12:2213-2215; Sun et al (2003) Bioorganic & Medicinal Chemistry 11:1761-1768; King et al (2002) Tetrahedron Letters 43:1987-1990). Dendritic linkers can increase the molar ratio of drug to antibody, i.e. loading, which is related to the potency of the ADC. Thus, where an antibody bears only one reactive cysteine thiol group, a multitude of drug moieties may be attached through a dendritic or branched linker.

One exemplary embodiment of a dendritic type linker has the structure:

where the asterisk indicate the point of attachment to the N10 position of a PBD moiety. R^(c), Capping Group

The conjugate of the first aspect of the invention may have a capping group R^(C) at the N10 position. Compound E may have a capping group R^(C).

In one embodiment, where the conjugate is a dimer with each monomer being of formula (A), the group R¹⁰ in one of the monomer units is a capping group R^(C) or is a group R¹⁰.

In one embodiment, where the conjugate is a dimer with each monomer being of formula (A), the group R¹⁰ in one of the monomer units is a capping group R^(C).

In one embodiment, where compound E is a dimer with each monomer being of formula (E), the group R^(L) in one of the monomer units is a capping group R^(C) or is a linker for connection to an antibody.

In one embodiment, where compound E is a dimer with each monomer being of formula (E), the group R^(L) in one of the monomer units is a capping group R^(C).

The group R^(C) is removable from the N10 position of the PBD moiety to leave an N10-C₁₁ imine bond, a carbinolamine, a substituted carbinolamine, where QR¹¹ is OSO₃M, a bisulfite adduct, a thiocarbinolamine, a substituted thiocarbinolamine, or a substituted carbinalamine.

In one embodiment, R^(C), may be a protecting group that is removable to leave an N10-C₁₁ imine bond, a carbinolamine, a substituted cabinolamine, or, where QR¹¹ is OSO₃M, a bisulfite adduct. In one embodiment, R^(C) is a protecting group that is removable to leave an N10-C₁₁ imine bond.

The group R^(c) is intended to be removable under the same conditions as those required for the removal of the group R¹⁰, for example to yield an N10-C₁₁ imine bond, a carbinolamine and so on. The capping group acts as a protecting group for the intended functionality at the N10 position. The capping group is intended not to be reactive towards an antibody. For example, R^(C) is not the same as R^(L).

Compounds having a capping group may be used as intermediates in the synthesis of dimers having an imine monomer. Alternatively, compounds having a capping group may be used as conjugates, where the capping group is removed at the target location to yield an imine, a carbinolamine, a substituted cabinolamine and so on. Thus, in this embodiment, the capping group may be referred to as a therapeutically removable nitrogen protecting group, as defined in the inventors' earlier application WO 00/12507.

In one embodiment, the group R^(C) is removable under the conditions that cleave the linker R^(L) of the group R¹⁰. Thus, in one embodiment, the capping group is cleavable by the action of an enzyme.

In an alternative embodiment, the capping group is removable prior to the connection of the linker R^(L) to the antibody. In this embodiment, the capping group is removable under conditions that do not cleave the linker R^(L).

Where a compound includes a functional group G¹ to form a connection to the antibody, the capping group is removable prior to the addition or unmasking of G¹.

The capping group may be used as part of a protecting group strategy to ensure that only one of the monomer units in a dimer is connected to an antibody.

The capping group may be used as a mask for a N10-C11 imine bond. The capping group may be removed at such time as the imine functionality is required in the compound. The capping group is also a mask for a carbinolamine, a substituted cabinolamine, and a bisulfite adduct, as described above.

R^(C) may be an N10 protecting group, such as those groups described in the inventors' earlier application, WO 00/12507. In one embodiment, R^(C) is a therapeutically removable nitrogen protecting group, as defined in the inventors' earlier application, WO 00/12507.

In one embodiment, R^(C) is a carbamate protecting group.

In one embodiment, the carbamate protecting group is selected from:

-   -   Alloc, Fmoc, Boc, Troc, Teoc, Psec, Cbz and PNZ.

Optionally, the carbamate protecting group is further selected from Moc.

In one embodiment, R^(C) is a linker group R^(L) lacking the functional group for connection to the antibody.

This application is particularly concerned with those R^(C) groups which are carbamates.

In one embodiment, R^(C) is a group:

-   -   where the asterisk indicates the point of attachment to the N10         position, G² is a terminating group, L³ is a covalent bond or a         cleavable linker L¹, L² is a covalent bond or together with         OC(═O) forms a self-immolative linker.

Where L³ and L² are both covalent bonds, G² and OC(═O) together form a carbamate protecting group as defined above.

L¹ is as defined above in relation to R¹⁰.

L² is as defined above in relation to R¹⁰.

Various terminating groups are described below, including those based on well known protecting groups.

In one embodiment L³ is a cleavable linker L¹, and L², together with OC(═O), forms a self-immolative linker. In this embodiment, G² is Ac (acetyl) or Moc, or a carbamate protecting group selected from:

-   -   Alloc, Fmoc, Boc, Troc, Teoc, Psec, Cbz and PNZ.

Optionally, the carbamate protecting group is further selected from Moc.

In another embodiment, G² is an acyl group —C(═O)G³, where G³ is selected from alkyl (including cycloalkyl, alkenyl and alkynyl), heteroalkyl, heterocyclyl and aryl (including heteroaryl and carboaryl). These groups may be optionally substituted. The acyl group together with an amino group of L³ or L², where appropriate, may form an amide bond. The acyl group together with a hydroxy group of L³ or L², where appropriate, may form an ester bond.

In one embodiment, G³ is heteroalkyl. The heteroalkyl group may comprise polyethylene glycol. The heteroalkyl group may have a heteroatom, such as O or N, adjacent to the acyl group, thereby forming a carbamate or carbonate group, where appropriate, with a heteroatom present in the group L³ or L², where appropriate.

In one embodiment, G³ is selected from NH₂, NHR and NRR′. Preferably, G³ is NRR′.

In one embodiment G² is the group:

-   -   where the asterisk indicates the point of attachment to L³, n is         0 to 6 and G⁴ is selected from OH, OR, SH, SR, COOR, CONH₂,         CONHR, CONRR′, NH₂, NHR, NRR′, NO₂, and halo. The groups OH, SH,         NH₂ and NHR are protected. In one embodiment, n is 1 to 6, and         preferably n is 5. In one embodiment, G⁴ is OR, SR, COOR, CONH₂,         CONHR, CONRR′, and NRR′. In one embodiment, G⁴ is OR, SR, and         NRR′. Preferably G⁴ is selected from OR and NRR′, most         preferably G⁴ is OR. Most preferably G⁴ is OMe.

In one embodiment, the group G² is:

-   -   where the asterisk indicates the point of attachment to L³, and         n and G⁴ are as defined above.

In one embodiment, the group G² is:

-   -   where the asterisk indicates the point of attachment to L³, n is         0 or 1, m is 0 to 50, and G⁴ is selected from OH, OR, SH, SR,         COOR, CONH₂, CONHR, CONRR′, NH₂, NHR, NRR′, NO₂, and halo. In a         preferred embodiment, n is 1 and m is 0 to 10, 1 to 2,         preferably 4 to 8, and most preferably 4 or 8. In another         embodiment, n is 1 and m is 10 to 50, preferably 20 to 40. The         groups OH, SH, NH₂ and NHR are protected. In one embodiment, G⁴         is OR, SR, COOR, CONH₂, CONHR, CONRR′, and NRR′. In one         embodiment, G⁴ is OR, SR, and NRR′. Preferably G⁴ is selected         from OR and NRR′, most preferably G⁴ is OR. Preferably G⁴ is         OMe.

In one embodiment, the group G² is:

-   -   where the asterisk indicates the point of attachment to L³, and         n, m and G⁴ are as defined above.

In one embodiment, the group G² is:

-   -   where n is 1-20, m is 0-6, and G⁴ is selected from OH, OR, SH,         SR, COOR, CONH₂, CONHR, CONRR′, NH₂, NHR, NRR′, NO₂, and halo.         In one embodiment, n is 1-10. In another embodiment, n is 10 to         50, preferably 20 to 40. In one embodiment, n is 1. In one         embodiment, m is 1. The groups OH, SH, NH₂ and NHR are         protected. In one embodiment, G⁴ is OR, SR, COOR, CONH₂, CONHR,         CONRR′, and NRR′. In one embodiment, G⁴ is OR, SR, and NRR′.         Preferably G⁴ is selected from OR and NRR′, most preferably G⁴         is OR. Preferably G⁴ is OMe.

In one embodiment, the group G² is:

-   -   where the asterisk indicates the point of attachment to L³, and         n, m and G⁴ are as defined above.

In each of the embodiments above G⁴ may be OH, SH, NH₂ and NHR. These groups are preferably protected.

In one embodiment, OH is protected with Bzl, TBDMS, or TBDPS.

In one embodiment, SH is protected with Acm, Bzl, Bzl-OMe, Bzl-Me, or Trt.

In one embodiment, NH₂ or NHR are protected with Boc, Moc, Z—Cl, Fmoc, Z, or Alloc.

In one embodiment, the group G² is present in combination with a group L³, which group is a dipeptide.

The capping group is not intended for connection to the antibody. Thus, the other monomer present in the dimer serves as the point of connection to the antibody via a linker. Accordingly, it is preferred that the functionality present in the capping group is not available for reaction with an antibody. Thus, reactive functional groups such as OH, SH, NH₂, COOH are preferably avoided. However, such functionality may be present in the capping group if protected, as described above.

EMBODIMENTS

Embodiments of the present invention include ConjA wherein the antibody is as defined above.

Embodiments of the present invention include ConjB wherein the antibody is as defined above.

Embodiments of the present invention include ConjC wherein the antibody is as defined above.

Embodiments of the present invention include ConjD wherein the antibody is as defined above.

Embodiments of the present invention include ConjE wherein the antibody is as defined above.

As mentioned above, some embodiments of the invention exclude ConjA, ConjB, ConjC, ConjD and ConjE.

Drug Loading

The drug loading is the average number of PBD drugs per antibody, e.g. antibody. Where the compounds of the invention are bound to cysteines, drug loading may range from 1 to 8 drugs (D^(L)) per antibody, i.e. where 1, 2, 3, 4, 5, 6, 7, and 8 drug moieties are covalently attached to the antibody. Compositions of conjugates include collections of antibodies, conjugated with a range of drugs, from 1 to 8. Where the compounds of the invention are bound to lysines, drug loading may range from 1 to 80 drugs (D^(L)) per antibody, although an upper limit of 40, 20, 10 or 8 may be preferred. Compositions of conjugates include collections of antibodies, conjugated with a range of drugs, from 1 to 80, 1 to 40, 1 to 20, 1 to 10 or 1 to 8.

The average number of drugs per antibody in preparations of ADC from conjugation reactions may be characterized by conventional means such as UV, reverse phase HPLC, HIC, mass spectroscopy, ELISA assay, and electrophoresis. The quantitative distribution of ADC in terms of p may also be determined. By ELISA, the averaged value of p in a particular preparation of ADC may be determined (Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070; Sanderson et al (2005) Clin. Cancer Res. 11:843-852). However, the distribution of p (drug) values is not discernible by the antibody-antigen binding and detection limitation of ELISA. Also, ELISA assay for detection of antibody-drug conjugates does not determine where the drug moieties are attached to the antibody, such as the heavy chain or light chain fragments, or the particular amino acid residues. In some instances, separation, purification, and characterization of homogeneous ADC where p is a certain value from ADC with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis. Such techniques are also applicable to other types of conjugates.

For some antibody-drug conjugates, p may be limited by the number of attachment sites on the antibody. For example, an antibody may have only one or several cysteine thiol groups, or may have only one or several sufficiently reactive thiol groups through which a linker may be attached. Higher drug loading, e.g. p>5, may cause aggregation, insolubility, toxicity, or loss of cellular permeability of certain antibody-drug conjugates.

Typically, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. An antibody may contain, for example, many lysine residues that do not react with the drug-linker intermediate (D-L) or linker reagent. Only the most reactive lysine groups may react with an amine-reactive linker reagent. Also, only the most reactive cysteine thiol groups may react with a thiol-reactive linker reagent. Generally, antibodies do not contain many, if any, free and reactive cysteine thiol groups which may be linked to a drug moiety. Most cysteine thiol residues in the antibodies of the compounds exist as disulfide bridges and must be reduced with a reducing agent such as dithiothreitol (DTT) or TCEP, under partial or total reducing conditions. The loading (drug/antibody ratio) of an ADC may be controlled in several different manners, including: (i) limiting the molar excess of drug-linker intermediate (D-L) or linker reagent relative to antibody, (ii) limiting the conjugation reaction time or temperature, and (iii) partial or limiting reductive conditions for cysteine thiol modification.

Certain antibodies have reducible interchain disulfides, i.e. cysteine bridges. Antibodies may be made reactive for conjugation with linker reagents by treatment with a reducing agent such as DTT (dithiothreitol). Each cysteine bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into antibodies through the reaction of lysines with 2-iminothiolane (Traut's reagent) resulting in conversion of an amine into a thiol. Reactive thiol groups may be introduced into the antibody (or fragment thereof) by engineering one, two, three, four, or more cysteine residues (e.g., preparing mutant antibodies comprising one or more non-native cysteine amino acid residues). U.S. Pat. No. 7,521,541 teaches engineering antibodies by introduction of reactive cysteine amino acids.

Cysteine amino acids may be engineered at reactive sites in an antibody and which do not form intrachain or intermolecular disulfide linkages (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. Nos. 7,521,541; 7,723,485; WO2009/052249). The engineered cysteine thiols may react with linker reagents or the drug-linker reagents of the present invention which have thiol-reactive, electrophilic groups such as maleimide or alpha-halo amides to form ADC with cysteine engineered antibodies and the PBD drug moieties. The location of the drug moiety can thus be designed, controlled, and known. The drug loading can be controlled since the engineered cysteine thiol groups typically react with thiol-reactive linker reagents or drug-linker reagents in high yield. Engineering an IgG antibody to introduce a cysteine amino acid by substitution at a single site on the heavy or light chain gives two new cysteines on the symmetrical antibody. A drug loading near 2 can be achieved with near homogeneity of the conjugation product ADC.

Alternatively, site-specific conjugation can be achieved by engineering antibodies to contain unnatural amino acids in their heavy and/or light chains as described by Axup et al. ((2012), Proc Natl Acad Sci USA. 109(40):16101-16116). The unnatural amino acids provide the additional advantage that orthogonal chemistry can be designed to attach the linker reagent and drug.

Where more than one nucleophilic or electrophilic group of the antibody reacts with a drug-linker intermediate, or linker reagent followed by drug moiety reagent, then the resulting product is a mixture of ADC compounds with a distribution of drug moieties attached to an antibody, e.g. 1, 2, 3, etc. Liquid chromatography methods such as polymeric reverse phase (PLRP) and hydrophobic interaction (HIC) may separate compounds in the mixture by drug loading value. Preparations of ADC with a single drug loading value (p) may be isolated, however, these single loading value ADCs may still be heterogeneous mixtures because the drug moieties may be attached, via the linker, at different sites on the antibody.

Thus the antibody-drug conjugate compositions of the invention include mixtures of antibody-drug conjugate compounds where the antibody has one or more PBD drug moieties and where the drug moieties may be attached to the antibody at various amino acid residues.

In one embodiment, the average number of dimer pyrrolobenzodiazepine groups per antibody is in the range 1 to 20. In some embodiments the range is selected from 1 to 8, 2 to 8, 2 to 6, 2 to 4, and 4 to 8.

In some embodiments, there is one dimer pyrrolobenzodiazepine group per antibody.

Includes Other Forms

Unless otherwise specified, included in the above are the well known ionic, salt, solvate, and protected forms of these substituents. For example, a reference to carboxylic acid (—COOH) also includes the anionic (carboxylate) form (—COO—), a salt or solvate thereof, as well as conventional protected forms. Similarly, a reference to an amino group includes the protonated form (—N⁺HR¹R²), a salt or solvate of the amino group, for example, a hydrochloride salt, as well as conventional protected forms of an amino group. Similarly, a reference to a hydroxyl group also includes the anionic form (—O⁻), a salt or solvate thereof, as well as conventional protected forms.

Salts

It may be convenient or desirable to prepare, purify, and/or handle a corresponding salt of the active compound, for example, a pharmaceutically-acceptable salt. Examples of pharmaceutically acceptable salts are discussed in Berge, et al., J. Pharm. Sci., 66, 1-19 (1977).

For example, if the compound is anionic, or has a functional group which may be anionic (e.g. —COOH may be —COO⁻), then a salt may be formed with a suitable cation. Examples of suitable inorganic cations include, but are not limited to, alkali metal ions such as Na⁺ and K⁺, alkaline earth cations such as Ca²⁺ and Mg²⁺, and other cations such as Al⁺³. Examples of suitable organic cations include, but are not limited to, ammonium ion (i.e. NH₄ ⁺) and substituted ammonium ions (e.g. NH₃R⁺, NH₂R²⁺, NHR₃ ⁺, NR₄ ⁺). Examples of some suitable substituted ammonium ions are those derived from: ethylamine, diethylamine, dicyclohexylamine, triethylamine, butylamine, ethylenediamine, ethanolamine, diethanolamine, piperazine, benzylamine, phenylbenzylamine, choline, meglumine, and tromethamine, as well as amino acids, such as lysine and arginine. An example of a common quaternary ammonium ion is N(CH₃)₄ ⁺.

If the compound is cationic, or has a functional group which may be cationic (e.g. —NH₂ may be —NH₃ ⁺), then a salt may be formed with a suitable anion. Examples of suitable inorganic anions include, but are not limited to, those derived from the following inorganic acids: hydrochloric, hydrobromic, hydroiodic, sulfuric, sulfurous, nitric, nitrous, phosphoric, and phosphorous.

Examples of suitable organic anions include, but are not limited to, those derived from the following organic acids: 2-acetyoxybenzoic, acetic, ascorbic, aspartic, benzoic, camphorsulfonic, cinnamic, citric, edetic, ethanedisulfonic, ethanesulfonic, fumaric, glucheptonic, gluconic, glutamic, glycolic, hydroxymaleic, hydroxynaphthalene carboxylic, isethionic, lactic, lactobionic, lauric, maleic, malic, methanesulfonic, mucic, oleic, oxalic, palmitic, pamoic, pantothenic, phenylacetic, phenylsulfonic, propionic, pyruvic, salicylic, stearic, succinic, sulfanilic, tartaric, toluenesulfonic, trifluoroacetic acid and valeric. Examples of suitable polymeric organic anions include, but are not limited to, those derived from the following polymeric acids: tannic acid, carboxymethyl cellulose.

Solvates

It may be convenient or desirable to prepare, purify, and/or handle a corresponding solvate of the active compound. The term “solvate” is used herein in the conventional sense to refer to a complex of solute (e.g. active compound, salt of active compound) and solvent. If the solvent is water, the solvate may be conveniently referred to as a hydrate, for example, a mono-hydrate, a di-hydrate, a tri-hydrate, etc.

The invention includes compounds where a solvent adds across the imine bond of the PBD moiety, which is illustrated below where the solvent is water or an alcohol (R^(A)OH, where R^(A) is C₁₋₄ alkyl):

These forms can be called the carbinolamine and carbinolamine ether forms of the PBD (as described in the section relating to R¹⁰ above). The balance of these equilibria depend on the conditions in which the compounds are found, as well as the nature of the moiety itself.

These particular compounds may be isolated in solid form, for example, by lyophilisation.

Isomers

Certain compounds of the invention may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r-forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and l-forms; (+) and (−) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; α- and β-forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as “isomers” (or “isomeric forms”).

The term “chiral” refers to molecules which have the property of non-superimposability of the mirror image partner, while the term “achiral” refers to molecules which are superimposable on their mirror image partner.

The term “stereoisomers” refers to compounds which have identical chemical constitution, but differ with regard to the arrangement of the atoms or groups in space.

“Diastereomer” refers to a stereoisomer with two or more centers of chirality and whose molecules are not mirror images of one another. Diastereomers have different physical properties, e.g. melting points, boiling points, spectral properties, and reactivities. Mixtures of diastereomers may separate under high resolution analytical procedures such as electrophoresis and chromatography.

“Enantiomers” refer to two stereoisomers of a compound which are non-superimposable mirror images of one another.

Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., “Stereochemistry of Organic Compounds”, John Wiley & Sons, Inc., New York, 1994. The compounds of the invention may contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms. It is intended that all stereoisomeric forms of the compounds of the invention, including but not limited to, diastereomers, enantiomers and atropisomers, as well as mixtures thereof such as racemic mixtures, form part of the present invention. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and l or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or l meaning that the compound is levorotatory. A compound prefixed with (+) or d is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which may occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity.

Note that, except as discussed below for tautomeric forms, specifically excluded from the term “isomers”, as used herein, are structural (or constitutional) isomers (i.e. isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, —OCH₃, is not to be construed as a reference to its structural isomer, a hydroxymethyl group, —CH₂OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta-chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g. C₁₋₇ alkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para-methoxyphenyl).

The above exclusion does not pertain to tautomeric forms, for example, keto-, enol-, and enolate-forms, as in, for example, the following tautomeric pairs: keto/enol (illustrated below), imine/enamine, amide/imino alcohol, amidine/amidine, nitroso/oxime, thioketone/enethiol, N-nitroso/hyroxyazo, and nitro/aci-nitro.

The term “tautomer” or “tautomeric form” refers to structural isomers of different energies which are interconvertible via a low energy barrier. For example, proton tautomers (also known as prototropic tautomers) include interconversions via migration of a proton, such as keto-enol and imine-enamine isomerizations. Valence tautomers include interconversions by reorganization of some of the bonding electrons.

Note that specifically included in the term “isomer” are compounds with one or more isotopic substitutions. For example, H may be in any isotopic form, including ¹H, ²H (D), and ³H (T); C may be in any isotopic form, including ¹²C, ¹³C, and ¹⁴C; O may be in any isotopic form, including ¹⁶O and ¹⁸O; and the like.

Examples of isotopes that can be incorporated into compounds of the invention include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, and chlorine, such as, but not limited to ²H (deuterium, D), ³H (tritium), ¹¹C, ¹³C, ¹⁴C ¹⁵N, ¹⁸F, ³¹P, ³²P, ³⁵S, ³⁶Cl, and ¹²⁵I. Various isotopically labeled compounds of the present invention, for example those into which radioactive isotopes such as 3H, 13C, and 14C are incorporated. Such isotopically labelled compounds may be useful in metabolic studies, reaction kinetic studies, detection or imaging techniques, such as positron emission tomography (PET) or single-photon emission computed tomography (SPECT) including drug or substrate tissue distribution assays, or in radioactive treatment of patients. Deuterium labelled or substituted therapeutic compounds of the invention may have improved DMPK (drug metabolism and pharmacokinetics) properties, relating to distribution, metabolism, and excretion (ADME). Substitution with heavier isotopes such as deuterium may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements. An 18F labeled compound may be useful for PET or SPECT studies. Isotopically labeled compounds of this invention and prodrugs thereof can generally be prepared by carrying out the procedures disclosed in the schemes or in the examples and preparations described below by substituting a readily available isotopically labeled reagent for a non-isotopically labeled reagent. Further, substitution with heavier isotopes, particularly deuterium (i.e., 2H or D) may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements or an improvement in therapeutic index. It is understood that deuterium in this context is regarded as a substituent. The concentration of such a heavier isotope, specifically deuterium, may be defined by an isotopic enrichment factor. In the compounds of this invention any atom not specifically designated as a particular isotope is meant to represent any stable isotope of that atom.

Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including (wholly or partially) racemic and other mixtures thereof. Methods for the preparation (e.g. asymmetric synthesis) and separation (e.g. fractional crystallisation and chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting the methods taught herein, or known methods, in a known manner.

Biological Activity

In Vitro Cell Proliferation Assays

Generally, the cytotoxic or cytostatic activity of an antibody-drug conjugate (ADC) is measured by: exposing mammalian cells having receptor proteins to the antibody of the ADC in a cell culture medium; culturing the cells for a period from about 6 hours to about 5 days; and measuring cell viability. Cell-based in vitro assays are used to measure viability (proliferation), cytotoxicity, and induction of apoptosis (caspase activation) of an ADC of the invention.

The in vitro potency of antibody-drug conjugates can be measured by a cell proliferation assay. The CellTiter-Glo® Luminescent Cell Viability Assay is a commercially available (Promega Corp., Madison, Wis.), homogeneous assay method based on the recombinant expression of Coleoptera luciferase (U.S. Pat. Nos. 5,583,024; 5,674,713 and 5,700,670). This cell proliferation assay determines the number of viable cells in culture based on quantitation of the ATP present, an indicator of metabolically active cells (Crouch et al (1993) J. Immunol. Meth. 160:81-88; U.S. Pat. No. 6,602,677). The CellTiter-Glo® Assay is conducted in 96 well format, making it amenable to automated high-throughput screening (HTS) (Cree et al (1995) AntiCancer Drugs 6:398-404). The homogeneous assay procedure involves adding the single reagent (CellTiter-Glo® Reagent) directly to cells cultured in serum-supplemented medium. Cell washing, removal of medium and multiple pipetting steps are not required. The system detects as few as 15 cells/well in a 384-well format in 10 minutes after adding reagent and mixing. The cells may be treated continuously with ADC, or they may be treated and separated from ADC. Generally, cells treated briefly, i.e. 3 hours, showed the same potency effects as continuously treated cells.

The homogeneous “add-mix-measure” format results in cell lysis and generation of a luminescent signal proportional to the amount of ATP present. The amount of ATP is directly proportional to the number of cells present in culture. The CellTiter-Glo® Assay generates a “glow-type” luminescent signal, produced by the luciferase reaction, which has a half-life generally greater than five hours, depending on cell type and medium used. Viable cells are reflected in relative luminescence units (RLU). The substrate, Beetle Luciferin, is oxidatively decarboxylated by recombinant firefly luciferase with concomitant conversion of ATP to AMP and generation of photons.

The in vitro potency of antibody-drug conjugates can also be measured by a cytotoxicity assay. Cultured adherent cells are washed with PBS, detached with trypsin, diluted in complete medium, containing 10% FCS, centrifuged, re-suspended in fresh medium and counted with a haemocytometer. Suspension cultures are counted directly. Monodisperse cell suspensions suitable for counting may require agitation of the suspension by repeated aspiration to break up cell clumps.

The cell suspension is diluted to the desired seeding density and dispensed (100 μl per well) into black 96 well plates. Plates of adherent cell lines are incubated overnight to allow adherence. Suspension cell cultures can be used on the day of seeding.

A stock solution (1 ml) of ADC (20 μg/ml) is made in the appropriate cell culture medium. Serial 10-fold dilutions of stock ADC are made in 15 ml centrifuge tubes by serially transferring 100 μl to 900 μl of cell culture medium.

Four replicate wells of each ADC dilution (100 μl) are dispensed in 96-well black plates, previously plated with cell suspension (100 μl), resulting in a final volume of 200 μl. Control wells receive cell culture medium (100 μl).

If the doubling time of the cell line is greater than 30 hours, ADC incubation is for 5 days, otherwise a four day incubation is done.

At the end of the incubation period, cell viability is assessed with the Alamar blue assay. AlamarBlue (Invitrogen) is dispensed over the whole plate (20 μl per well) and incubated for 4 hours. Alamar blue fluorescence is measured at excitation 570 nm, emission 585 nm on the Varioskan flash plate reader. Percentage cell survival is calculated from the mean fluorescence in the ADC treated wells compared to the mean fluorescence in the control wells.

Use

The conjugates of the invention may be used to provide a PBD compound at a target location.

The target location is preferably a proliferative cell population. The antibody is an antibody for an antigen present on a proliferative cell population.

In one embodiment the antigen is absent or present at a reduced level in a non-proliferative cell population compared to the amount of antigen present in the proliferative cell population, for example a tumour cell population.

At the target location the linker may be cleaved so as to release a compound RelA, RelB, RelC, RelD or RelE. Thus, the conjugate may be used to selectively provide a compound RelA, RelB, Rel C, RelD or RelE to the target location.

The linker may be cleaved by an enzyme present at the target location.

The target location may be in vitro, in vivo or ex vivo.

The antibody-drug conjugate (ADC) compounds of the invention include those with utility for anticancer activity. In particular, the compounds include an antibody conjugated, i.e. covalently attached by a linker, to a PBD drug moiety, i.e. toxin. When the drug is not conjugated to an antibody, the PBD drug has a cytotoxic effect. The biological activity of the PBD drug moiety is thus modulated by conjugation to an antibody. The antibody-drug conjugates (ADC) of the invention selectively deliver an effective dose of a cytotoxic agent to tumor tissue whereby greater selectivity, i.e. a lower efficacious dose, may be achieved.

Thus, in one aspect, the present invention provides a conjugate compound as described herein for use in therapy.

In a further aspect there is also provides a conjugate compound as described herein for use in the treatment of a proliferative disease. A second aspect of the present invention provides the use of a conjugate compound in the manufacture of a medicament for treating a proliferative disease.

One of ordinary skill in the art is readily able to determine whether or not a candidate conjugate treats a proliferative condition for any particular cell type. For example, assays which may conveniently be used to assess the activity offered by a particular compound are described in the examples below.

The term “proliferative disease” pertains to an unwanted or uncontrolled cellular proliferation of excessive or abnormal cells which is undesired, such as, neoplastic or hyperplastic growth, whether in vitro or in vivo.

Examples of proliferative conditions include, but are not limited to, benign, pre-malignant, and malignant cellular proliferation, including but not limited to, neoplasms and tumours (e.g. histocytoma, glioma, astrocyoma, osteoma), cancers (e.g. lung cancer, small cell lung cancer, gastrointestinal cancer, bowel cancer, colon cancer, breast carinoma, ovarian carcinoma, prostate cancer, testicular cancer, liver cancer, kidney cancer, bladder cancer, pancreas cancer, brain cancer, sarcoma, osteosarcoma, Kaposi's sarcoma, melanoma), lymphomas, leukemias, psoriasis, bone diseases, fibroproliferative disorders (e.g. of connective tissues), and atherosclerosis. Cancers of particular interest include, but are not limited to, leukemias and ovarian cancers.

Any type of cell may be treated, including but not limited to, lung, gastrointestinal (including, e.g. bowel, colon), breast (mammary), ovarian, prostate, liver (hepatic), kidney (renal), bladder, pancreas, brain, and skin.

Disorders of particular interest include, but are not limited to, non-Hodgkin Lymphoma, including diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, (FL), Mantle Cell lymphoma (MCL), chronic lymphatic lymphoma (CLL) and leukemias such as Hairy cell leukemia (HCL), Hairy cell leukemia variant (HCL-v) and Acute Lymphoblastic Leukaemia (ALL).

It is contemplated that the antibody-drug conjugates (ADC) of the present invention may be used to treat various diseases or disorders, e.g. characterized by the overexpression of a tumor antigen. Exemplary conditions or hyperproliferative disorders include benign or malignant tumors; leukemia, haematological, and lymphoid malignancies. Others include neuronal, glial, astrocytal, hypothalamic, glandular, macrophagal, epithelial, stromal, blastocoelic, inflammatory, angiogenic and immunologic, including autoimmune, disorders.

Generally, the disease or disorder to be treated is a hyperproliferative disease such as cancer. Examples of cancer to be treated herein include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia or lymphoid malignancies. More particular examples of such cancers include squamous cell cancer (e.g. epithelial squamous cell cancer), lung cancer including small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung and squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, rectal cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney or renal cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, anal carcinoma, penile carcinoma, as well as head and neck cancer.

Autoimmune diseases for which the ADC compounds may be used in treatment include rheumatologic disorders (such as, for example, rheumatoid arthritis, Sjögren's syndrome, scleroderma, lupus such as SLE and lupus nephritis, polymyositis/dermatomyositis, cryoglobulinemia, anti-phospholipid antibody syndrome, and psoriatic arthritis), osteoarthritis, autoimmune gastrointestinal and liver disorders (such as, for example, inflammatory bowel diseases (e.g. ulcerative colitis and Crohn's disease), autoimmune gastritis and pernicious anemia, autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and celiac disease), vasculitis (such as, for example, ANCA-associated vasculitis, including Churg-Strauss vasculitis, Wegener's granulomatosis, and polyarteriitis), autoimmune neurological disorders (such as, for example, multiple sclerosis, opsoclonus myoclonus syndrome, myasthenia gravis, neuromyelitis optica, Parkinson's disease, Alzheimer's disease, and autoimmune polyneuropathies), renal disorders (such as, for example, glomerulonephritis, Goodpasture's syndrome, and Berger's disease), autoimmune dermatologic disorders (such as, for example, psoriasis, urticaria, hives, pemphigus vulgaris, bullous pemphigoid, and cutaneous lupus erythematosus), hematologic disorders (such as, for example, thrombocytopenic purpura, thrombotic thrombocytopenic purpura, post-transfusion purpura, and autoimmune hemolytic anemia), atherosclerosis, uveitis, autoimmune hearing diseases (such as, for example, inner ear disease and hearing loss), Behcet's disease, Raynaud's syndrome, organ transplant, and autoimmune endocrine disorders (such as, for example, diabetic-related autoimmune diseases such as insulin-dependent diabetes mellitus (IDDM), Addison's disease, and autoimmune thyroid disease (e.g. Graves' disease and thyroiditis)). More preferred such diseases include, for example, rheumatoid arthritis, ulcerative colitis, ANCA-associated vasculitis, lupus, multiple sclerosis, Sjögren's syndrome, Graves' disease, IDDM, pernicious anemia, thyroiditis, and glomerulonephritis.

Methods of Treatment

The conjugates of the present invention may be used in a method of therapy. Also provided is a method of treatment, comprising administering to a subject in need of treatment a therapeutically-effective amount of a conjugate compound of the invention. The term “therapeutically effective amount” is an amount sufficient to show benefit to a patient. Such benefit may be at least amelioration of at least one symptom. The actual amount administered, and rate and time-course of administration, will depend on the nature and severity of what is being treated. Prescription of treatment, e.g. decisions on dosage, is within the responsibility of general practitioners and other medical doctors.

A compound of the invention may be administered alone or in combination with other treatments, either simultaneously or sequentially dependent upon the condition to be treated. Examples of treatments and therapies include, but are not limited to, chemotherapy (the administration of active agents, including, e.g. drugs, such as chemotherapeutics); surgery; and radiation therapy.

A “chemotherapeutic agent” is a chemical compound useful in the treatment of cancer, regardless of mechanism of action. Classes of chemotherapeutic agents include, but are not limited to: alkylating agents, antimetabolites, spindle poison plant alkaloids, cytotoxic/antitumor antibiotics, topoisomerase inhibitors, antibodies, photosensitizers, and kinase inhibitors. Chemotherapeutic agents include compounds used in “targeted therapy” and conventional chemotherapy.

Examples of chemotherapeutic agents include: erlotinib (TARCEVA®, Genentech/OSI Pharm.), docetaxel (TAXOTERE®, Sanofi-Aventis), 5-FU (fluorouracil, 5-fluorouracil, CAS No. 51-21-8), gemcitabine (GEMZAR®, Lilly), PD-0325901 (CAS No. 391210-10-9, Pfizer), cisplatin (cis-diamine, dichloroplatinum(II), CAS No. 15663-27-1), carboplatin (CAS No. 41575-94-4), paclitaxel (TAXOL®, Bristol-Myers Squibb Oncology, Princeton, N.J.), trastuzumab (HERCEPTIN®, Genentech), temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4.3.0]nona-2,7,9-triene-9-carboxamide, CAS No. 85622-93-1, TEMODAR®, TEMODAL®, Schering Plough), tamoxifen ((Z)-2-[4-(1,2-diphenylbut-1-enyl)phenoxy]-N,N-dimethylethanamine, NOLVADEX®, ISTUBAL®, VALODEX®), and doxorubicin (ADRIAMYCIN®), Akti-1/2, HPPD, and rapamycin.

More examples of chemotherapeutic agents include: oxaliplatin (ELOXATIN®, Sanofi), bortezomib (VELCADE®, Millennium Pharm.), sutent (SUNITINIB®, SU11248, Pfizer), letrozole (FEMARA®, Novartis), imatinib mesylate (GLEEVEC®, Novartis), XL-518 (Mek inhibitor, Exelixis, WO 2007/044515), ARRY-886 (Mek inhibitor, AZD6244, Array BioPharma, Astra Zeneca), SF-1126 (PI3K inhibitor, Semafore Pharmaceuticals), BEZ-235 (PI3K inhibitor, Novartis), XL-147 (PI3K inhibitor, Exelixis), PTK787/ZK 222584 (Novartis), fulvestrant (FASLODEX®, AstraZeneca), leucovorin (folinic acid), rapamycin (sirolimus, RAPAMUNE®, Wyeth), lapatinib (TYKERB®, GSK572016, Glaxo Smith Kline), lonafarnib (SARASAR™, SCH 66336, Schering Plough), sorafenib (NEXAVAR®, BAY43-9006, Bayer Labs), gefitinib (IRESSA®, AstraZeneca), irinotecan (CAMPTOSAR®, CPT-11, Pfizer), tipifarnib (ZARNESTRA™, Johnson & Johnson), ABRAXANE™ (Cremophor-free), albumin-engineered nanoparticle formulations of paclitaxel (American Pharmaceutical Partners, Schaumberg, II), vandetanib (rlNN, ZD6474, ZACTIMA®, AstraZeneca), chloranmbucil, AG1478, AG1571 (SU 5271; Sugen), temsirolimus (TORISEL®, Wyeth), pazopanib (GlaxoSmithKline), canfosfamide (TELCYTA®, Telik), thiotepa and cyclosphosphamide (CYTOXAN®, NEOSAR®); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylomelamine; acetogenins (especially bullatacin and bullatacinone); a camptothecin (including the synthetic analog topotecan); bryostatin; callystatin; CC-1065 (including its adozelesin, carzelesin and bizelesin synthetic analogs); cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogs, KW-2189 and CB1-TM1); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, chlorophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e.g. calicheamicin, calicheamicin gamma1I, calicheamicin omegal1 (Angew Chem. Intl. Ed. Engl. (1994) 33:183-186); dynemicin, dynemicin A; bisphosphonates, such as clodronate; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycinis, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, nemorubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogs such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; podophyllinic acid; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, Oreg.); razoxane; rhizoxin; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2,2′,2″-trichlorotriethylamine; trichothecenes (especially T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine; dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (“Ara-C”); cyclophosphamide; thiotepa; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine; vinorelbine (NAVELBINE®); novantrone; teniposide; edatrexate; daunomycin; aminopterin; capecitabine (XELODA®, Roche); ibandronate; CPT-11; topoisomerase inhibitor RFS 2000; difluoromethylornithine (DMFO); retinoids such as retinoic acid; and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are: (i) anti-hormonal agents that act to regulate or inhibit hormone action on tumors such as anti-estrogens and selective estrogen receptor modulators (SERMs), including, for example, tamoxifen (including NOLVADEX®; tamoxifen citrate), raloxifene, droloxifene, 4-hydroxytamoxifen, trioxifene, keoxifene, LY117018, onapristone, and FARESTON® (toremifine citrate); (ii) aromatase inhibitors that inhibit the enzyme aromatase, which regulates estrogen production in the adrenal glands, such as, for example, 4(5)-imidazoles, aminoglutethimide, MEGASE® (megestrol acetate), AROMASIN® (exemestane; Pfizer), formestanie, fadrozole, RIVISOR® (vorozole), FEMARA® (letrozole; Novartis), and ARIMIDEX® (anastrozole; AstraZeneca); (iii) anti-androgens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin; as well as troxacitabine (a 1,3-dioxolane nucleoside cytosine analog); (iv) protein kinase inhibitors such as MEK inhibitors (WO 2007/044515); (v) lipid kinase inhibitors; (vi) antisense oligonucleotides, particularly those which inhibit expression of genes in signaling pathways implicated in aberrant cell proliferation, for example, PKC-alpha, Raf and H-Ras, such as oblimersen (GENASENSE®, Genta Inc.); (vii) ribozymes such as VEGF expression inhibitors (e.g., ANGIOZYME®) and HER2 expression inhibitors; (viii) vaccines such as gene therapy vaccines, for example, ALLOVECTIN®, LEUVECTIN®, and VAXID®; PROLEUKIN® rIL-2; topoisomerase 1 inhibitors such as LURTOTECAN®; ABARELIX® rmRH; (ix) anti-angiogenic agents such as bevacizumab (AVASTIN®, Genentech); and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are therapeutic antibodies such as alemtuzumab (Campath), bevacizumab (AVASTIN®, Genentech); cetuximab (ERBITUX®, Imclone); panitumumab (VECTIBIX®, Amgen), rituximab (RITUXAN®, Genentech/Biogen Idec), ofatumumab (ARZERRA®, GSK), pertuzumab (PERJETA™, OMNITARG™, 2C₄, Genentech), trastuzumab (HERCEPTIN®, Genentech), tositumomab (Bexxar, Corixia), and the antibody drug conjugate, gemtuzumab ozogamicin (MYLOTARG®, Wyeth).

Humanized monoclonal antibodies with therapeutic potential as chemotherapeutic agents in combination with the conjugates of the invention include: alemtuzumab, apolizumab, aselizumab, atlizumab, bapineuzumab, bevacizumab, bivatuzumab mertansine, cantuzumab mertansine, cedelizumab, certolizumab pegol, cidfusituzumab, cidtuzumab, daclizumab, eculizumab, efalizumab, epratuzumab, erlizumab, felvizumab, fontolizumab, gemtuzumab ozogamicin, inotuzumab ozogamicin, ipilimumab, labetuzumab, lintuzumab, matuzumab, mepolizumab, motavizumab, motovizumab, natalizumab, nimotuzumab, nolovizumab, numavizumab, ocrelizumab, omalizumab, palivizumab, pascolizumab, pecfusituzumab, pectuzumab, pertuzumab, pexelizumab, ralivizumab, ranibizumab, reslivizumab, reslizumab, resyvizumab, rovelizumab, ruplizumab, sibrotuzumab, siplizumab, sontuzumab, tacatuzumab tetraxetan, tadocizumab, talizumab, tefibazumab, tocilizumab, toralizumab, trastuzumab, tucotuzumab celmoleukin, tucusituzumab, umavizumab, urtoxazumab, and visilizumab.

Pharmaceutical compositions according to the present invention, and for use in accordance with the present invention, may comprise, in addition to the active ingredient, i.e. a conjugate compound, a pharmaceutically acceptable excipient, carrier, buffer, stabiliser or other materials well known to those skilled in the art. Such materials should be non-toxic and should not interfere with the efficacy of the active ingredient. The precise nature of the carrier or other material will depend on the route of administration, which may be oral, or by injection, e.g. cutaneous, subcutaneous, or intravenous.

Pharmaceutical compositions for oral administration may be in tablet, capsule, powder or liquid form. A tablet may comprise a solid carrier or an adjuvant. Liquid pharmaceutical compositions generally comprise a liquid carrier such as water, petroleum, animal or vegetable oils, mineral oil or synthetic oil. Physiological saline solution, dextrose or other saccharide solution or glycols such as ethylene glycol, propylene glycol or polyethylene glycol may be included. A capsule may comprise a solid carrier such a gelatin.

For intravenous, cutaneous or subcutaneous injection, or injection at the site of affliction, the active ingredient will be in the form of a parenterally acceptable aqueous solution which is pyrogen-free and has suitable pH, isotonicity and stability. Those of relevant skill in the art are well able to prepare suitable solutions using, for example, isotonic vehicles such as Sodium Chloride Injection, Ringer's Injection, Lactated Ringer's Injection. Preservatives, stabilisers, buffers, antioxidants and/or other additives may be included, as required.

Formulations

While it is possible for the conjugate compound to be used (e.g., administered) alone, it is often preferable to present it as a composition or formulation.

In one embodiment, the composition is a pharmaceutical composition (e.g., formulation, preparation, medicament) comprising a conjugate compound, as described herein, and a pharmaceutically acceptable carrier, diluent, or excipient.

In one embodiment, the composition is a pharmaceutical composition comprising at least one conjugate compound, as described herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, including, but not limited to, pharmaceutically acceptable carriers, diluents, excipients, adjuvants, fillers, buffers, preservatives, anti-oxidants, lubricants, stabilisers, solubilisers, surfactants (e.g., wetting agents), masking agents, colouring agents, flavouring agents, and sweetening agents.

In one embodiment, the composition further comprises other active agents, for example, other therapeutic or prophylactic agents.

Suitable carriers, diluents, excipients, etc. can be found in standard pharmaceutical texts. See, for example, Handbook of Pharmaceutical Additives, 2nd Edition (eds. M. Ash and I. Ash), 2001 (Synapse Information Resources, Inc., Endicott, N.Y., USA), Remington's Pharmaceutical Sciences, 20th edition, pub. Lippincott, Williams & Wilkins, 2000; and Handbook of Pharmaceutical Excipients, 2nd edition, 1994.

Another aspect of the present invention pertains to methods of making a pharmaceutical composition comprising admixing at least one [¹¹C]-radiolabelled conjugate or conjugate-like compound, as defined herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, e.g., carriers, diluents, excipients, etc. If formulated as discrete units (e.g., tablets, etc.), each unit contains a predetermined amount (dosage) of the active compound.

The term “pharmaceutically acceptable,” as used herein, pertains to compounds, ingredients, materials, compositions, dosage forms, etc., which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of the subject in question (e.g., human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. Each carrier, diluent, excipient, etc. must also be “acceptable” in the sense of being compatible with the other ingredients of the formulation.

The formulations may be prepared by any methods well known in the art of pharmacy. Such methods include the step of bringing into association the active compound with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active compound with carriers (e.g., liquid carriers, finely divided solid carrier, etc.), and then shaping the product, if necessary.

The formulation may be prepared to provide for rapid or slow release; immediate, delayed, timed, or sustained release; or a combination thereof.

Formulations suitable for parenteral administration (e.g., by injection), include aqueous or non-aqueous, isotonic, pyrogen-free, sterile liquids (e.g., solutions, suspensions), in which the active ingredient is dissolved, suspended, or otherwise provided (e.g., in a liposome or other microparticulate). Such liquids may additional contain other pharmaceutically acceptable ingredients, such as anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, suspending agents, thickening agents, and solutes which render the formulation isotonic with the blood (or other relevant bodily fluid) of the intended recipient. Examples of excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like. Examples of suitable isotonic carriers for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection. Typically, the concentration of the active ingredient in the liquid is from about 1 ng/ml to about 10 μg/ml, for example from about 10 ng/ml to about 1 μg/ml. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets.

Dosage

It will be appreciated by one of skill in the art that appropriate dosages of the conjugate compound, and compositions comprising the conjugate compound, can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health, and prior medical history of the patient. The amount of compound and route of administration will ultimately be at the discretion of the physician, veterinarian, or clinician, although generally the dosage will be selected to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects.

Administration can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell(s) being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician, veterinarian, or clinician.

In general, a suitable dose of the active compound is in the range of about 100 ng to about mg (more typically about 1 μg to about 10 mg) per kilogram body weight of the subject per day. Where the active compound is a salt, an ester, an amide, a prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 100 mg, 3 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 150 mg, 2 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 200 mg, 2 times daily.

However in one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 50 or about 75 mg, 3 or 4 times daily.

In one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 100 or about 125 mg, 2 times daily.

The dosage amounts described above may apply to the conjugate (including the PBD moiety and the linker to the antibody) or to the effective amount of PBD compound provided, for example the amount of compound that is releasable after cleavage of the linker.

For the prevention or treatment of disease, the appropriate dosage of an ADC of the invention will depend on the type of disease to be treated, as defined above, the severity and course of the disease, whether the molecule is administered for preventive or therapeutic purposes, previous therapy, the patient's clinical history and response to the antibody, and the discretion of the attending physician. The molecule is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the disease, about 1 μg/kg to 15 mg/kg (e.g. 0.1-20 mg/kg) of molecule is an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. A typical daily dosage might range from about 1 μg/kg to 100 mg/kg or more, depending on the factors mentioned above. An exemplary dosage of ADC to be administered to a patient is in the range of about 0.1 to about 10 mg/kg of patient weight. For repeated administrations over several days or longer, depending on the condition, the treatment is sustained until a desired suppression of disease symptoms occurs. An exemplary dosing regimen comprises a course of administering an initial loading dose of about 4 mg/kg, followed by additional doses every week, two weeks, or three weeks of an ADC. Other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

Treatment

The term “treatment,” as used herein in the context of treating a condition, pertains generally to treatment and therapy, whether of a human or an animal (e.g., in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, regression of the condition, amelioration of the condition, and cure of the condition. Treatment as a prophylactic measure (i.e., prophylaxis, prevention) is also included.

The term “therapeutically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Similarly, the term “prophylactically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired prophylactic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Preparation of Drug Conjugates

Antibody drug conjugates may be prepared by several routes, employing organic chemistry reactions, conditions, and reagents known to those skilled in the art, including reaction of a nucleophilic group of an antibody with a drug-linker reagent. This method may be employed to prepare the antibody-drug conjugates of the invention.

Nucleophilic groups on antibodies include, but are not limited to side chain thiol groups, e.g. cysteine. Thiol groups are nucleophilic and capable of reacting to form covalent bonds with electrophilic groups on linker moieties such as those of the present invention. Certain antibodies have reducible interchain disulfides, i.e. cysteine bridges. Antibodies may be made reactive for conjugation with linker reagents by treatment with a reducing agent such as DTT (Cleland's reagent, dithiothreitol) or TCEP (tris(2-carboxyethyl)phosphine hydrochloride; Getz et al (1999) Anal. Biochem. Vol 273:73-80; Soltec Ventures, Beverly, Mass.). Each cysteine disulfide bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into antibodies through the reaction of lysines with 2-iminothiolane (Traut's reagent) resulting in conversion of an amine into a thiol.

The Subject/Patient

The subject/patient may be an animal, mammal, a placental mammal, a marsupial (e.g., kangaroo, wombat), a monotreme (e.g., duckbilled platypus), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., a bird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., a cow), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orangutang, gibbon), or a human.

Furthermore, the subject/patient may be any of its forms of development, for example, a foetus. In one preferred embodiment, the subject/patient is a human.

Further Preferences

The following preferences may apply to all aspects of the invention as described above, or may relate to a single aspect. The preferences may be combined together in any combination.

In some embodiments, R^(6′), R^(7′), R^(9′), and Y′ are preferably the same as R⁶, R⁷, R⁹, and Y respectively.

Dimer Link

Y and Y′ are preferably O.

R″ is preferably a C₃₋₇ alkylene group with no substituents. More preferably R″ is a C₃, C₅ or C₇ alkylene. Most preferably, R″ is a C₃ or C₅ alkylene.

R⁶ to R⁹

R⁹ is preferably H.

R⁶ is preferably selected from H, OH, OR, SH, NH₂, nitro and halo, and is more preferably H or halo, and most preferably is H.

R⁷ is preferably selected from H, OH, OR, SH, SR, NH₂, NHR, NRR′, and halo, and more preferably independently selected from H, OH and OR, where R is preferably selected from optionally substituted C₁₋₇ alkyl, C₃₋₁₀ heterocyclyl and C₅₋₁₀ aryl groups. R may be more preferably a C₁₋₄ alkyl group, which may or may not be substituted. A substituent of interest is a C₅₋₆ aryl group (e.g. phenyl). Particularly preferred substituents at the 7-positions are OMe and OCH₂Ph. Other substituents of particular interest are dimethylamino (i.e. —NMe₂); —(OC₂H₄)_(q)OMe, where q is from 0 to 2; nitrogen-containing C₆ heterocyclyls, including morpholino, piperidinyl and N-methyl-piperazinyl.

These preferences apply to R^(9′), R^(6′) and R^(7′) respectively.

R¹²

When there is a double bond present between C2′ and C3′, R¹² is selected from:

(a) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene;

(b) C₁₋₅ saturated aliphatic alkyl;

(c) C₃₋₆ saturated cycloalkyl;

(d)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (e)

wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl; and (f)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl.

When R¹² is a C₅₋₁₀ aryl group, it may be a C₅₋₇ aryl group. A C₅₋₇ aryl group may be a phenyl group or a C₅₋₇ heteroaryl group, for example furanyl, thiophenyl and pyridyl. In some embodiments, R¹² is preferably phenyl. In other embodiments, R¹² is preferably thiophenyl, for example, thiophen-2-yl and thiophen-3-yl.

When R¹² is a C₅₋₁₀ aryl group, it may be a C₈₋₁₀ aryl, for example a quinolinyl or isoquinolinyl group. The quinolinyl or isoquinolinyl group may be bound to the PBD core through any available ring position. For example, the quinolinyl may be quinolin-2-yl, quinolin-3-yl, quinolin-4yl, quinolin-5-yl, quinolin-6-yl, quinolin-7-yl and quinolin-8-yl. Of these quinolin-3-yl and quinolin-6-yl may be preferred. The isoquinolinyl may be isoquinolin-1-yl, isoquinolin-3-yl, isoquinolin-4yl, isoquinolin-5-yl, isoquinolin-6-yl, isoquinolin-7-yl and isoquinolin-8-yl. Of these isoquinolin-3-yl and isoquinolin-6-yl may be preferred.

When R¹² is a C₅₋₁₀ aryl group, it may bear any number of substituent groups. It preferably bears from 1 to 3 substituent groups, with 1 and 2 being more preferred, and singly substituted groups being most preferred. The substituents may be any position.

Where R¹² is C₅₋₇ aryl group, a single substituent is preferably on a ring atom that is not adjacent the bond to the remainder of the compound, i.e. it is preferably β or γ to the bond to the remainder of the compound. Therefore, where the C₅₋₇ aryl group is phenyl, the substituent is preferably in the meta- or para-positions, and more preferably is in the para-position.

Where R¹² is a C₈₋₁₀ aryl group, for example quinolinyl or isoquinolinyl, it may bear any number of substituents at any position of the quinoline or isoquinoline rings. In some embodiments, it bears one, two or three substituents, and these may be on either the proximal and distal rings or both (if more than one substituent).

R¹² Substituents, when R¹² is a C₅₋₁₀ Aryl Group

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is halo, it is preferably F or Cl, more preferably Cl.

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is ether, it may in some embodiments be an alkoxy group, for example, a C₁₋₇ alkoxy group (e.g. methoxy, ethoxy) or it may in some embodiments be a C₅₋₇ aryloxy group (e.g phenoxy, pyridyloxy, furanyloxy). The alkoxy group may itself be further substituted, for example by an amino group (e.g. dimethylamino).

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is C₁₋₇ alkyl, it may preferably be a C₁₋₄ alkyl group (e.g. methyl, ethyl, propryl, butyl).

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is C₃₋₇ heterocyclyl, it may in some embodiments be C₆ nitrogen containing heterocyclyl group, e.g. morpholino, thiomorpholino, piperidinyl, piperazinyl. These groups may be bound to the rest of the PBD moiety via the nitrogen atom. These groups may be further substituted, for example, by C₁₋₄ alkyl groups. If the C₆ nitrogen containing heterocyclyl group is piperazinyl, the said further substituent may be on the second nitrogen ring atom.

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is bis-oxy-C₁₋₃ alkylene, this is preferably bis-oxy-methylene or bis-oxy-ethylene.

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is ester, this is preferably methyl ester or ethyl ester.

Particularly preferred substituents when R¹² is a C₅₋₁₀ aryl group include methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methylthiophenyl. Other particularly preferred substituent for R¹² are dimethylaminopropyloxy and carboxy.

Particularly preferred substituted R¹² groups when R¹² is a C₅₋₁₀ aryl group include, but are not limited to, 4-methoxy-phenyl, 3-methoxyphenyl, 4-ethoxy-phenyl, 3-ethoxy-phenyl, 4-fluoro-phenyl, 4-chloro-phenyl, 3,4-bisoxymethylene-phenyl, 4-methylthiophenyl, 4-cyanophenyl, 4-phenoxyphenyl, quinolin-3-yl and quinolin-6-yl, isoquinolin-3-yl and isoquinolin-6-yl, 2-thienyl, 2-furanyl, methoxynaphthyl, and naphthyl. Another possible substituted R¹² group is 4-nitrophenyl. R¹² groups of particular interest include 4-(4-methylpiperazin-1-yl)phenyl and 3,4-bisoxymethylene-phenyl.

When R¹² is C₁₋₅ saturated aliphatic alkyl, it may be methyl, ethyl, propyl, butyl or pentyl. In some embodiments, it may be methyl, ethyl or propyl (n-pentyl or isopropyl). In some of these embodiments, it may be methyl. In other embodiments, it may be butyl or pentyl, which may be linear or branched.

When R¹² is C₃₋₆ saturated cycloalkyl, it may be cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. In some embodiments, it may be cyclopropyl.

When R¹² is

each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5. In some embodiments, the total number of carbon atoms in the R¹² group is no more than 4 or no more than 3.

In some embodiments, one of R²¹, R²² and R²³ is H, with the other two groups being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In other embodiments, two of R²¹, R²² and R²³ are H, with the other group being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In some embodiments, the groups that are not H are selected from methyl and ethyl. In some of these embodiments, the groups that re not H are methyl.

In some embodiments, R²¹ is H.

In some embodiments, R²² is H.

In some embodiments, R²³ is H.

In some embodiments, R²¹ and R²² are H.

In some embodiments, R²¹ and R²³ are H.

In some embodiments, R²² and R²³ are H.

An R¹² group of particular interest is:

When R¹² is

one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl. In some embodiments, the group which is not H is optionally substituted phenyl. If the phenyl optional substituent is halo, it is preferably fluoro. In some embodiment, the phenyl group is unsubstituted.

When R¹² is

R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl. If the phenyl optional substituent is halo, it is preferably fluoro. In some embodiment, the phenyl group is unsubstituted.

In some embodiments, R²⁴ is selected from H, methyl, ethyl, ethenyl and ethynyl. In some of these embodiments, R²⁴ is selected from H and methyl.

When there is a single bond present between C2′ and C3′,

R¹² is

where R^(26a) and R^(2b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester.

In some embodiments, it is preferred that R^(26a) and R^(26b) are both H.

In other embodiments, it is preferred that R^(26a) and R^(26b) are both methyl.

In further embodiments, it is preferred that one of R^(26a) and R^(26b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted. In these further embodiment, it may be further preferred that the group which is not H is selected from methyl and ethyl.

R²

The above preferences for R¹² apply equally to R².

R²²

In some embodiments, R²² is of formula IIa.

A in R²² when it is of formula IIa may be phenyl group or a C₅₋₇ heteroaryl group, for example furanyl, thiophenyl and pyridyl. In some embodiments, A is preferably phenyl.

Q²-X may be on any of the available ring atoms of the C₅₋₇ aryl group, but is preferably on a ring atom that is not adjacent the bond to the remainder of the compound, i.e. it is preferably β or γ to the bond to the remainder of the compound. Therefore, where the C₅₋₇ aryl group (A) is phenyl, the substituent (Q²-X) is preferably in the meta- or para-positions, and more preferably is in the para-position.

In some embodiments, Q¹ is a single bond. In these embodiments, Q² is selected from a single bond and —Z—(CH₂)_(n)—, where Z is selected from a single bond, O, S and NH and is from 1 to 3. In some of these embodiments, Q² is a single bond. In other embodiments, Q² is —Z—(CH₂)_(n)—. In these embodiments, Z may be O or S and n may be 1 or n may be 2. In other of these embodiments, Z may be a single bond and n may be 1.

In other embodiments, Q¹ is —CH═CH—.

In other embodiments, R²² is of formula IIb. In these embodiments, R^(C1), R^(C2) and R^(C3) are independently selected from H and unsubstituted C₁₋₂ alkyl. In some preferred embodiments, R_(C1), R^(C2) and R^(C3) are all H. In other embodiments, R_(C1), R^(C2) and R^(C3) are all methyl. In certain embodiments, R_(C1), R^(C2) and R^(C3) are independently selected from H and methyl.

X is a group selected from the list comprising: O—R^(L2′), S—R^(L2′), CO₂—R^(L2′), CO—R^(L2′), NH—C(═O)—R^(L2′), NHNH—R^(L2′), CONHNH—R^(L2′),

NR^(N)R^(L2′), wherein R^(N) is selected from the group comprising H and C₁₋₄ alkyl. X may preferably be: OH, SH, CO₂H, —N═C═O or NHR^(N), and may more preferably be: O—R^(L2′), S—R^(L2′), CO₂—R^(L2′), —NH—C(═O)—R^(L2′) or NH—R^(L2′). Particularly preferred groups include: O—R^(L2′), S—R^(L2′) and NH—R^(L2′), with NH—R^(L2′) being the most preferred group.

In some embodiments R²² is of formula IIc. In these embodiments, it is preferred that Q is NR^(N)—R^(L2′). In other embodiments, Q is O—R^(L2′). In further embodiments, Q is S—R^(L2′). R^(N) is preferably selected from H and methyl. In some embodiment, R^(N) is H. In other embodiments, R^(N) is methyl.

In some embodiments, R²² may be -A-CH₂—X and -A-X. In these embodiments, X may be O—R^(L2′), S—R^(L2′), CO₂—R^(L2′), CO—R^(L2′) and NH—R^(L2′). In particularly preferred embodiments, X may be NH—R^(L2′).

R¹⁰, R¹¹

In some embodiments, R¹⁰ and R¹¹ together form a double bond between the nitrogen and carbon atoms to which they are bound.

In some embodiments, R¹¹ is OH.

In some embodiments, R¹¹ is OMe.

In some embodiments, R¹¹ is SO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation.

R^(11a)

In some embodiments, R^(11a) is OH.

In some embodiments, R^(11a) is OMe.

In some embodiments, R^(11a) is SO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation.

R²⁰, R²¹

In some embodiments, R²⁰ and R²¹ together form a double bond between the nitrogen and carbon atoms to which they are bound.

In some embodiments R²⁰ is H.

In some embodiments, R²⁰ is R^(C).

In some embodiments, R²¹ is OH.

In some embodiments, R²¹ is OMe.

In some embodiments, R²¹ is SO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation.

R³⁰, R³¹

In some embodiments, R³⁰ and R³¹ together form a double bond between the nitrogen and carbon atoms to which they are bound.

In some embodiments, R³¹ is OH.

In some embodiments, R³¹ is OMe.

In some embodiments, R³¹ is SO_(z)M, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation.

M and z

It is preferred that M is a monovalent pharmaceutically acceptable cation, and is more preferably Na⁺.

z is preferably 3.

Preferred conjugates of the first aspect of the present invention may have a D^(L) of formula Ia:

where R^(L1′), R²⁰ and R²¹ are as defined above; n is 1 or 3; R^(1a) is methyl or phenyl; and R^(2a) is selected from: (a)

(b)

(c)

(d)

(e)

(f)

(g)

and (h)

Preferred conjugates of the first aspect of the present invention may have a D^(L) of formula Ib:

where R^(L1′), R²⁰ and R²¹ are as defined above; n is 1 or 3; and R^(1a) is methyl or phenyl.

Preferred conjugates of the first aspect of the present invention may have a D^(L) of formula Ic:

where R^(L2′), R¹⁰, R¹¹, R³⁰ and R³¹ are as defined above n is 1 or 3; R^(12a) is selected from: (a)

(b)

(c)

(d)

(e)

(f)

(g)

and (h)

the amino group is at either the meta or para positions of the phenyl group.

Preferred conjugates of the first aspect of the present invention may have a D^(L) of formula Id:

where R^(L2′), R¹⁰, R¹¹, R³⁰ and R³¹ are as defined above n is 1 or 3; R^(1a) is methyl or phenyl; R^(12a) is selected from: (a)

(b)

(c)

(d)

(e)

(f)

(g)

and (h)

Preferred conjugates of the first aspect of the present invention may have a D^(L) of formula Ie:

where R^(L2′), R¹⁰, R¹¹, R³⁰ and R³¹ are as defined above n is 1 or 3; R^(1a) is methyl or phenyl; R^(12a) is selected from: (a)

(b)

(c)

(d)

(e)

(f)

(g)

and (h)

EXAMPLES

General Experimental Methods

Optical rotations were measured on an ADP 220 polarimeter (Bellingham Stanley Ltd.) and concentrations (c) are given in g/100 mL. Melting points were measured using a digital melting point apparatus (Electrothermal). IR spectra were recorded on a Perkin-Elmer Spectrum 1000 FT IR Spectrometer. ¹H and ¹³C NMR spectra were acquired at 300 K using a Bruker Avance NMR spectrometer at 400 and 100 MHz, respectively. Chemical shifts are reported relative to TMS (δ=0.0 ppm), and signals are designated as s (singlet), d (doublet), t (triplet), dt (double triplet), dd (doublet of doublets), ddd (double doublet of doublets) or m (multiplet), with coupling constants given in Hertz (Hz). Mass spectroscopy (MS) data were collected using a Waters Micromass ZQ instrument coupled to a Waters 2695 HPLC with a Waters 2996 PDA. Waters Micromass ZQ parameters used were: Capillary (kV), 3.38; Cone (V), 35; Extractor (V), 3.0; Source temperature (° C.), 100; Desolvation Temperature (° C.), 200; Cone flow rate (L/h), 50; De-solvation flow rate (L/h), 250. High-resolution mass spectroscopy (HRMS) data were recorded on a Waters Micromass QTOF Global in positive W-mode using metal-coated borosilicate glass tips to introduce the samples into the instrument. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄), and flash chromatography utilised silica gel (Merck 60, 230-400 mesh ASTM). Except for the HOBt (NovaBiochem) and solid-supported reagents (Argonaut), all other chemicals and solvents were purchased from Sigma-Aldrich and were used as supplied without further purification. Anhydrous solvents were prepared by distillation under a dry nitrogen atmosphere in the presence of an appropriate drying agent, and were stored over 4 Å molecular sieves or sodium wire. Petroleum ether refers to the fraction boiling at 40-60° C.

General LC/MS Conditions:

Method 1 (Default Method, Used Unless Stated Otherwise)

The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B held over 1.0 min, then increase from 5% B to 95% B over a 3 min period. The composition was held for 0.1 min at 95% B, then returned to 5% B in 0.03 minutes and hold there for 0.87 min. Total gradient run time equals 5 minutes.

Method 2

The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B held over 1.0 minute, then increase from 5% B to 95% B over a 2.5 minute period. The composition was held for 0.5 minutes at 95% B, then returned to 5% B in 0.1 minutes and hold there for 0.9 min. Total gradient run time equals 5 minutes.

For Both Methods

Flow rate 3.0 mL/min, 400 μL was split via a zero dead volume tee piece which passes into the mass spectrometer. Wavelength detection range: 220 to 400 nm. Function type: diode array (535 scans). Column: Phenomenex Onyx Monolithic C₁₈ 50×4.60 mm.

The reverse phase flash purification conditions were as follows: The Flash purification system (Varian 971-Fp) was run using a mobile phase of water (A) and acetonitrile (B). Gradient: initial composition 5% B over 20 C.V. (Column Volume) then 5% B to 70% B within 60 C.V. The composition was held for 15 C.V. at 95% B, and then returned to 5% B in 5 C.V. and held at 5% B for 10 C.V. Total gradient run time equals 120 C.V. Flow rate 6.0 mL/min. Wavelength detection range: 254 nm. Column: Agilent AX1372-1 SF10-5.5gC8.

Preparative HPLC: Reverse-phase ultra-high-performance liquid chromatography (UPLC) was carried out on Phenomenex Gemini NX 5μ C-18 columns of the following dimensions: 150×4.6 mm for analysis, and 150×21.20 mm for preparative work. All UPLC experiments were performed with gradient conditions. Eluents used were solvent A (H₂O with 0.1% Formic acid) and solvent B (CH₃CN with 0.1% Formic acid). Flow rates used were 1.0 ml/min for analytical, and 20.0 ml/min for preparative HPLC. Detection was at 254 and 280 nm.

Synthesis of Intermediate 12

(a) 1′,3′-Bis[2-methoxy-4-(methoxycarbonyl)phenoxy]propane (3)

Diisopropyl azodicarboxylate (71.3 mL, 73.2 g, 362 mmol) was added drop-wise over a period of 60 min to an overhead stirred solution of methyl vanillate 2 (60.0 g, 329 mmol) and Ph₃P (129.4 g, 494 mmol) in anhydrous THF (800 mL) at 0-5° C. (ice/acetone) under a nitrogen atmosphere. The reaction mixture was allowed to stir at 0-5° C. for an additional 1 hour after which time a solution of 1,3-propanediol (11.4 mL, 12.0 g, 158 mmol) in THF (12 mL) was added drop-wise over a period of 20 min. The reaction mixture was allowed to warm to room temperature and stirred for 5 days. The resulting white precipitate 3 was collected by vacuum filtration, washed with THF and dried in a vacuum desiccator to constant weight. Yield=54.7 g (84% based on 1,3-propanediol). Purity satisfactory by LC/MS (3.20 min (ES+) m/z (relative intensity) 427 ([M+Na]⁺, 10); ¹H NMR (400 MHz, CDCl₃) δ 7.64 (dd, 2H, J=1.8, 8.3 Hz), 7.54 (d, 2H, J=1.8 Hz), 6.93 (d, 2H, J=8.5 Hz), 4.30 (t, 4H, J=6.1 Hz), 3.90 (s, 6H), 3.89 (s, 6H), 2.40 (p, 2H, J=6.0 Hz).

(b) 1′,3′-Bis[2-methoxy-4-(methoxycarbonyl)-5-nitrophenoxy]propane (4)

Solid Cu(NO₃)₂.3H₂O (81.5 g, 337.5 mmol) was added slowly to an overhead stirred slurry of the bis-ester 3 (54.7 g, 135 mmol) in acetic anhydride (650 mL) at 0-5° C. (ice/acetone). The reaction mixture was allowed to stir for 1 hour at 0-5° C. and then allowed to warm to room temperature. A mild exotherm (ca. 40-50° C.), accompanied by thickening of the mixture and evolution of NO₂ was observed at this stage. Additional acetic anhydride (300 mL) was added and the reaction mixture was allowed to stir for 16 hours at room temperature. The reaction mixture was poured on to ice (˜1.5 L), stirred and allowed to return to room temperature. The resulting yellow precipitate was collected by vacuum filtration and dried in a desiccator to afford the desired bis-nitro compound 4 as a yellow solid. Yield=66.7 g (100%). Purity satisfactory by LC/MS (3.25 min (ES+) m/z (relative intensity) 517 ([M+Na]⁺, 40); ¹H NMR (400 MHz, CDCl₃) δ 7.49 (s, 2H), 7.06 (s, 2H), 4.32 (t, 4H, J=6.0 Hz), 3.95 (s, 6H), 3.90 (s, 6H), 2.45-2.40 (m, 2H).

(c) 1′,3′-Bis(4-carboxy-2-methoxy-5-nitrophenoxy) Propane (5)

A slurry of the methyl ester 4 (66.7 g, 135 mmol) in THF (700 mL) was treated with 1N NaOH (700 mL) and the reaction mixture was allowed to stir vigorously at room temperature. After 4 days stirring, the slurry became a dark coloured solution which was subjected to rotary evaporation under reduced pressure to remove THF. The resulting aqueous residue was acidified to pH 1 with concentrated HCl and the colourless precipitate 5 was collected and dried thoroughly in a vacuum oven (50° C.). Yield=54.5 g (87%). Purity satisfactory by LC/MS (2.65 min (ES+) m/z (relative intensity) 489 ([M+Na]⁺, 30)); ¹H NMR (400 MHz, DMSO-d₆) δ 7.62 (s, 2H), 7.30 (s, 2H), 4.29 (t, 4H, J=6.0 Hz), 3.85 (s, 6H), 2.30-2.26 (m, 2H).

(d) 1,1′-[[(Propane-1,3-diyl)dioxy]bis[(5-methoxy-2-nitro-1,4-phenylene)carbonyl]]bis[(2S,4R)-methyl-4-hydroxypyrrolidine-2-carboxylate](6)

Oxalyl chloride (24.5 mL, 35.6 g, 281 mmol) was added to a stirred suspension of the nitrobenzoic acid 5 (43 g, 92.3 mmol) and DMF (6 mL) in anhydrous DCM (600 mL). Following initial effervescence the reaction suspension became a solution and the mixture was allowed to stir at room temperature for 16 hours. Conversion to the acid chloride was confirmed by treating a sample of the reaction mixture with MeOH and the resulting bis-methyl ester was observed by LC/MS. The majority of solvent was removed by evaporation under reduced pressure; the resulting concentrated solution was re-dissolved in a minimum amount of dry DCM and triturated with diethyl ether. The resulting yellow precipitate was collected by filtration, washed with cold diethyl ether and dried for 1 hour in a vacuum oven at 40° C. The solid acid chloride was added portionwise over a period of 25 min to a stirred suspension of (2S,4R)-methyl-4-hydroxypyrrolidine-2-carboxylate hydrochloride (38.1 g, 210 mmol) and TEA (64.5 mL, g, 463 mmol) in DCM (400 mL) at −40° C. (dry ice/CH₃CN). Immediately, the reaction was complete as judged by LC/MS (2.47 min (ES+) m/z (relative intensity) 721 ([M+H]⁺, 100). The mixture was diluted with DCM (200 mL) and washed with 1N HCl (300 mL), saturated NaHCO₃ (300 mL), brine (400 mL), dried (MgSO₄), filtered and the solvent evaporated in vacuo to give the pure product 6 as an orange solid (66.7 g, 100%). [α]²² _(D)=−46.1° (c=0.47, CHCl₃); ¹H NMR (400 MHz, CDCl₃) (rotamers) δ 7.63 (s, 2H), 6.82 (s, 2H), 4.79-4.72 (m, 2H), 4.49-4.28 (m, 6H), 3.96 (s, 6H), 3.79 (s, 6H), 3.46-3.38 (m, 2H), 3.02 (d, 2H, J=11.1 Hz), 2.48-2.30 (m, 4H), 2.29-2.04 (m, 4H); ¹³C NMR (100 MHz, CDCl₃) (rotamers) δ 172.4, 166.7, 154.6, 148.4, 137.2, 127.0, 109.7, 108.2, 69.7, 65.1, 57.4, 57.0, 56.7, 52.4, 37.8, 29.0; IR (ATR, CHCl₃) 3410 (br), 3010, 2953, 1741, 1622, 1577, 1519, 1455, 1429, 1334, 1274, 1211, 1177, 1072, 1050, 1008, 871 cm⁻¹; MS (ES⁺) m/z (relative intensity) 721 ([M+H]⁺, 47), 388 (80); HRMS [M+H]⁺. theoretical C₃₁H₃₆N₄O₁₆ m/z 721.2199. found (ES⁺) m/z 721.2227.

(e) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(hydroxy)-7-methoxy-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione](7)

Method A:

A solution of the nitro-ester 6 (44 g, 61.1 mmol) in MeOH (2.8 L) was added to freshly purchased Raney® nickel (˜50 g of a ˜50% slurry in H₂O) and anti-bumping granules in a 5 L 3-neck round bottomed flask. The mixture was heated at reflux and then treated dropwise with a solution of hydrazine hydrate (21.6 mL, 22.2 g, 693 mmol) in MeOH (200 mL) at which point vigorous effervescence was observed. When the addition was complete (˜45 min) additional Raney® nickel was added carefully until effervescence had ceased and the initial yellow colour of the reaction mixture was discharged. The mixture was heated at reflux for a further 5 min at which point the reaction was deemed complete by TLC (90:10 v/v CHCl₃/MeOH) and LC/MS (2.12 min (ES+) m/z (relative intensity) 597 ([M+H]⁺, 100)). The reaction mixture was filtered hot immediately through a sinter funnel containing celite with vacuum suction. The filtrate was reduced in volume by evaporation in vacuo at which point a colourless precipitate formed which was collected by filtration and dried in a vacuum desiccator to provide 7 (31 g, 85%). [α]²⁷D=+404° (c=0.10, DMF); ¹H NMR (400 MHz, DMSO-d₆) δ 10.2 (s, 2H, NH), 7.26 (s, 2H), 6.73 (s, 2H), 5.11 (d, 2H, J=3.98 Hz, OH), 4.32-4.27 (m, 2H), 4.19-4.07 (m, 6H), 3.78 (s, 6H), 3.62 (dd, 2H, J=12.1, 3.60 Hz), 3.43 (dd, 2H, J=12.0, 4.72 Hz), 2.67-2.57 (m, 2H), 2.26 (p, 2H, J=5.90 Hz), 1.99-1.89 (m, 2H); ¹³C NMR (100 MHz, DMSO-d₆) δ 169.1, 164.0, 149.9, 144.5, 129.8, 117.1, 111.3, 104.5, 54.8, 54.4, 53.1, 33.5, 27.5; IR (ATR, neat) 3438, 1680, 1654, 1610, 1605, 1516, 1490, 1434, 1379, 1263, 1234, 1216, 1177, 1156, 1115, 1089, 1038, 1018, 952, 870 cm⁻¹; MS (ES⁺) m/z (relative intensity) 619 ([M+Na]⁺, 10), 597 ([M+H]⁺, 52), 445 (12), 326 (11); HRMS [M+H]⁺. theoretical C₂₉H₃₂N₄O₁₀ m/z 597.2191. found (ES⁺) m/z 597.2205.

Method B:

A suspension of 10% Pd/C (7.5 g, 10% w/w) in DMF (40 mL) was added to a solution of the nitro-ester 6 (75 g, 104 mmol) in DMF (360 mL). The suspension was hydrogenated in a Parr hydrogenation apparatus over 8 hours. Progress of the reaction was monitored by LC/MS after the hydrogen uptake had stopped. Solid Pd/C was removed by filtration and the filtrate was concentrated by rotary evaporation under vacuum (below 10 mbar) at 40° C. to afford a dark oil containing traces of DMF and residual charcoal. The residue was digested in EtOH (500 mL) at 40° C. on a water bath (rotary evaporator bath) and the resulting suspension was filtered through celite and washed with ethanol (500 mL) to give a clear filtrate. Hydrazine hydrate (10 mL, 321 mmol) was added to the solution and the reaction mixture was heated at reflux. After 20 minutes the formation of a white precipitate was observed and reflux was allowed to continue for a further 30 minutes. The mixture was allowed to cool down to room temperature and the precipitate was retrieved by filtration, washed with diethyl ether (2:1 volume of precipitate) and dried in a vacuum desiccator to provide 7 (50 g, 81%). Analytical data for method B: Identical to those obtained for Method A (optical rotation, ¹H NMR, LC/MS and TLC).

(f) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(tert-butyldimethylsilyloxy)-7-methoxy-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione](8)

TBSCl (27.6 g, 182.9 mmol) and imidazole (29.9 g, 438.8 mmol) were added to a cloudy solution of the tetralactam 7 (21.8 g, 36.6 mmol) in anhydrous DMF (400 mL) at 0° C. (ice/acetone). The mixture was allowed to stir under a nitrogen atmosphere for 3 hours after which time the reaction was deemed complete as judged by LC/MS (3.90 min (ES+) m/z (relative intensity) 825 ([M+H]⁺, 100). The reaction mixture was poured onto ice (˜1.75 L) and allowed to warm to room temperature with stirring. The resulting white precipitate was collected by vacuum filtration, washed with H₂O, diethyl ether and dried in the vacuum desicator to provide pure 8 (30.1 g, 99%). [α]²³D=+234° (c=0.41, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 8.65 (s, 2H, NH), 7.44 (s, 2H), 6.54 (s, 2H), 4.50 (p, 2H, J=5.38 Hz), 4.21-4.10 (m, 6H), 3.87 (s, 6H), 3.73-3.63 (m, 4H), 2.85-2.79 (m, 2H), 2.36-2.29 (m, 2H), 2.07-1.99 (m, 2H), 0.86 (s, 18H), 0.08 (s, 12H); ¹³C NMR (100 MHz, CDCl₃) δ 170.4, 165.7, 151.4, 146.6, 129.7, 118.9, 112.8, 105.3, 69.2, 65.4, 56.3, 55.7, 54.2, 35.2, 28.7, 25.7, 18.0, −4.82 and −4.86; IR (ATR, CHCl₃) 3235, 2955, 2926, 2855, 1698, 1695, 1603, 1518, 1491, 1446, 1380, 1356, 1251, 1220, 1120, 1099, 1033 cm⁻¹; MS (ES⁺) m/z (relative intensity) 825 ([M+H]⁺, 62), 721 (14), 440 (38); HRMS [M+H]. theoretical C₄₁H₆₀N₄O₁₀Si₂ m/z 825.3921. found (ES⁺) m/z 825.3948.

(g) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-(tert-butyldimethylsilyloxy)-7-methoxy-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (9)

A solution of n-BuLi (68.3 mL of a 1.6 M solution in hexane, 109 mmol) was added dropwise to a stirred suspension of the tetralactam 8 (30.08 g, 36.4 mmol) in anhydrous THF (600 mL) at −30° C. (dry ice/ethylene glycol) under a nitrogen atmosphere. The reaction mixture was allowed to stir at this temperature for 1 hour (now a reddish orange colour) at which point a solution of SEMCl (19.3 mL, 18.2 g, 109 mmol) in anhydrous THF (120 mL) was added dropwise. The reaction mixture was allowed to slowly warm to room temperature and was stirred for 16 hours under a nitrogen atmosphere. The reaction was deemed complete as judged by TLC (EtOAc) and LC/MS (4.77 min (ES+) m/z (relative intensity) 1085 ([M+H]⁺, 100). The THF was removed by evaporation in vacuo and the resulting residue dissolved in EtOAc (750 mL), washed with H₂O (250 mL), brine (250 mL), dried (MgSO₄) filtered and evaporated in vacuo to provide the crude N10-SEM-protected tetralactam 9 as an oil (max^(m) 39.5 g, 100%). Product carried through to next step without purification. [α]²³D=+163α (c=0.41, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.33 (s, 2H), 7.22 (s, 2H), 5.47 (d, 2H, J=9.98 Hz), 4.68 (d, 2H, J=9.99 Hz), 4.57 (p, 2H, J=5.77 Hz), 4.29-4.19 (m, 6H), 3.89 (s, 6H), 3.79-3.51 (m, 8H), 2.87-2.81 (m, 2H), 2.41 (p, 2H, J=5.81 Hz), 2.03-1.90 (m, 2H), 1.02-0.81 (m, 22H), 0.09 (s, 12H), 0.01 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 170.0, 165.7, 151.2, 147.5, 133.8, 121.8, 111.6, 106.9, 78.1, 69.6, 67.1, 65.5, 56.6, 56.3, 53.7, 35.6, 30.0, 25.8, 18.4, 18.1, −1.24, −4.73; IR (ATR, CHCl₃) 2951, 1685, 1640, 1606, 1517, 1462, 1433, 1360, 1247, 1127, 1065 cm⁻¹; MS (ES⁺) m/z (relative intensity) 1113 ([M+Na]⁺, 48), 1085 ([M+H]⁺, 100), 1009 (5), 813 (6); HRMS [M+H]⁺ theoretical C₅₃H₈₈N₄O₁₂Si₄ m/z 1085.5548. found (ES⁺) m/z 1085.5542.

(h) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS,2R)-2-hydroxy-7-methoxy-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] (10)

A solution of TBAF (150 mL of a 1.0 M solution in THF, 150 mmol) was added to a stirred solution of the crude bis-silyl ether 9 [84.0 g (max^(m) 56.8 g), 52.4 mmol] in THF (800 mL) at room temperature. After stirring for 1 hour, analysis of the reaction mixture by TLC (95:5 v/v CHCl₃/MeOH) revealed completion of reaction. The THF was removed by evaporation under reduced pressure at room temperature and the resulting residue dissolved in EtOAc (500 mL) and washed with NH₄Cl (300 mL). The combined organic layers were washed with brine (60 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 100% CHCl₃ to 96:4 v/v CHCl₃/MeOH) gave the pure tetralactam 10 as a white foam (36.0 g, 79%). LC/MS 3.33 min (ES+) m/z (relative intensity) 879 ([M+Na]₊, 100), 857 ([M+H]⁺, 40); [α]²³D=+2020 (c=0.34, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.28 (s, 2H), 7.20 (s, 2H), 5.44 (d, 2H, J=10.0 Hz), 4.72 (d, 2H, J=10.0 Hz), 4.61-4.58 (m, 2H), 4.25 (t, 4H, J=5.83 Hz), 4.20-4.16 (m, 2H), 3.91-3.85 (m, 8H), 3.77-3.54 (m, 6H), 3.01 (br s, 2H, OH), 2.96-2.90 (m, 2H), 2.38 (p, 2H, J=5.77 Hz), 2.11-2.05 (m, 2H), 1.00-0.91 (m, 4H), 0.00 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 169.5, 165.9, 151.3, 147.4, 133.7, 121.5, 111.6, 106.9, 79.4, 69.3, 67.2, 65.2, 56.5, 56.2, 54.1, 35.2, 29.1, 18.4, −1.23; IR (ATR, CHCl₃) 2956, 1684, 1625, 1604, 1518, 1464, 1434, 1361, 1238, 1058, 1021 cm⁻¹; MS (ES⁺) m/z (relative intensity) 885 ([M+29]⁺, 70), 857 ([M+H]⁺, 100), 711 (8), 448 (17); HRMS [M+H]⁺. theoretical C₄₁H₆₀N4O₁₂Si₂ m/z 857.3819. found (ES⁺) m/z 857.3826.

(i) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS)-7-methoxy-2-oxo-10-((2-(trimethylsilyl)ethoxy)methyl)-1,2,3,10,11,11a-hexahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione](11)

Diol 10 (25.6 g, 30 mmol, 1 eq.), NaOAc (6.9 g, 84 mmol, 2.8 eq.) and TEMPO (188 mg, 1.2 mmol, 0.04 eq.) were dissolved in DCM (326 mL) under Ar. This was cooled to −8° C. (internal temperature) and TCCA (9.7 g, 42 mmol, 1.4 eq.) was added portionwise over 15 minutes. TLC (EtOAc) and LC/MS [3.60 min. (ES+) m/z (relative intensity) 854.21 ([M+H]⁺, 40), (ES−) m/z (relative intensity) 887.07 ([M−H+Cl]⁻, 10)] after 30 minutes indicated that reaction was complete. Cold DCM (200 mL) was added and the mixture was filtered through a pad of Celite before washing with a solution of saturated sodium hydrogen carbonate/sodium thiosulfate (1:1 v/v; 200 mL×2). The organic layer was dried with MgSO₄, filtered and the solvent removed in vacuo to yield a yellow/orange sponge (25.4 g, 99%). LC/MS [3.60 min. (ES+) m/z (relative intensity) 854.21 ([M+H]⁺, 40); [α]²⁰ _(D)=+291° (c=0.26, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.32 (s, 2H), 7.25 (s, 2H), 5.50 (d, 2H, J=10.1 Hz), 4.75 (d, 2H, J=10.1 Hz), 4.60 (dd, 2H, J=9.85, 3.07 Hz), 4.31-4.18 (m, 6H), 3.89-3.84 (m, 8H), 3.78-3.62 (m, 4H), 3.55 (dd, 2H, J=19.2, 2.85 Hz), 2.76 (dd, 2H, J=19.2, 9.90 Hz), 2.42 (p, 2H, J=5.77 Hz), 0.98-0.91 (m, 4H), 0.00 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 206.8, 168.8, 165.9, 151.8, 148.0, 133.9, 120.9, 111.6, 107.2, 78.2, 67.3, 65.6, 56.3, 54.9, 52.4, 37.4, 29.0, 18.4, −1.24; IR (ATR, CHCl₃) 2957, 1763, 1685, 1644, 1606, 1516, 1457, 1434, 1360, 1247, 1209, 1098, 1066, 1023 cm⁻¹; MS (ES⁺) m/z (relative intensity) 881 ([M+29]⁺, 38), 853 ([M+H]⁺, 100), 707 (8), 542 (12); HRMS [M+H]⁺. theoretical C₄₁H₅₆N4O₁₂Si₂ m/z 853.3506. found (ES⁺) m/z 853.3502.

(j) 1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS)-7-methoxy-2-[[(trifluoromethyl)sulfonyl]oxy]-10-((2-(trimethylsilyl)ethoxy)methyl)-1,10,11,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione](12)

Anhydrous 2,6-lutidine (5.15 mL, 4.74 g, 44.2 mmol) was injected in one portion to a vigorously stirred solution of bis-ketone 11 (6.08 g, 7.1 mmol) in dry DCM (180 mL) at −45° C. (dry ice/acetonitrile) under a nitrogen atmosphere. Anhydrous triflic anhydride, taken from a freshly opened ampoule (7.2 mL, 12.08 g, 42.8 mmol), was injected rapidly dropwise, while maintaining the temperature at −40° C. or below. The reaction mixture was allowed to stir at −45° C. for 1 hour at which point TLC (50/50 v/v n-hexane/EtOAc) revealed the complete consumption of starting material. The cold reaction mixture was immediately diluted with DCM (200 mL) and, with vigorous shaking, washed with water (1×100 mL), 5% citric acid solution (1×200 mL) saturated NaHCO₃ (200 mL), brine (100 mL) and dried (MgSO₄). Filtration and evaporation of the solvent under reduced pressure afforded the crude product which was purified by flash column chromatography (gradient elution: 90:10 v/v n-hexane/EtOAc to 70:30 v/v n-hexane/EtOAc) to afford bis-enol triflate 12 as a yellow foam (5.5 g, 70%). LC/MS 4.32 min (ES+) m/z (relative intensity) 1139 ([M+Na]⁺, 20); [α]²⁴ _(D)=+271° (c=0.18, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.33 (s, 2H), 7.26 (s, 2H), 7.14 (t, 2H, J=1.97 Hz), 5.51 (d, 2H, J=10.1 Hz), 4.76 (d, 2H, J=10.1 Hz), 4.62 (dd, 2H, J=11.0, 3.69 Hz), 4.32-4.23 (m, 4H), 3.94-3.90 (m, 8H), 3.81-3.64 (m, 4H), 3.16 (ddd, 2H, J=16.3, 11.0, 2.36 Hz), 2.43 (p, 2H, J=5.85 Hz), 1.23-0.92 (m, 4H), 0.02 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 167.1, 162.7, 151.9, 148.0, 138.4, 133.6, 120.2, 118.8, 111.9, 107.4, 78.6, 67.5, 65.6, 56.7, 56.3, 30.8, 29.0, 18.4, −1.25; IR (ATR, CHCl₃) 2958, 1690, 1646, 1605, 1517, 1456, 1428, 1360, 1327, 1207, 1136, 1096, 1060, 1022, 938, 913 cm⁻¹; MS (ES⁺) m/z (relative intensity) 1144 ([M+28]⁺, 100), 1117 ([M+H]⁺, 48), 1041 (40), 578 (8); HRMS [M+H]⁺. theoretical C₄₃H₅₄N₄O₁₆Si₂S₂F₆ m/z 1117.2491. found (ES⁺) m/z 1117.2465.

Example 1

(a) (S)-8-(3-(((S)-2-(4-aminophenyl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl trifluoromethanesulfonate (13)

Pd(PPh₃)₄ (116.9 mg, 0.101 mmol) was added to a stirred mixture of the bis-enol triflate 12 (5.65 g, 5.06 mmol), 4-Aminophenylboronic acid pinacol ester (1 g, 4.56 mmol), Na₂CO₃ (2.46 g, 23.2 mmol), MeOH (37 mL), toluene (74 mL) and water (37 mL). The reaction mixture was allowed to stir at 30° C. under a nitrogen atmosphere for 24 hours after which time all the boronic ester has consumed. The reaction mixture was then evaporated to dryness before the residue was taken up in EtOAc (150 mL) and washed with H₂O (2×100 mL), brine (150 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 80:20 v/v Hexane/EtOAc to 60:40 v/v Hexane/EtOAc) afforded product 13 as a yellowish foam (2.4 g, 45%). LC/MS 4.02 min (ES+) m/z (relative intensity) 1060.21 ([M+H]⁺, 100); ¹H-NMR: (CDCl₃, 400 MHz) δ 7.40 (s, 1H), 7.33 (s, 1H), 7.27 (bs, 3H), 7.24 (d, 2H, J=8.5 Hz), 7.15 (t, 1H, J=2.0 Hz), 6.66 (d, 2H, J=8.5 Hz), 5.52 (d, 2H, J=10.0 Hz), 4.77 (d, 1H, J=10.0 Hz), 4.76 (d, 1H, J=10.0 Hz), 4.62 (dd, 1H, J=3.7, 11.0 Hz), 4.58 (dd, 1H, J=3.4, 10.6 Hz), 4.29 (t, 4H, J=5.6 Hz), 4.00-3.85 (m, 8H), 3.80-3.60 (m, 4H), 3.16 (ddd, 1H, J=2.4, 11.0, 16.3 Hz), 3.11 (ddd, 1H, J=2.2, 10.5, 16.1 Hz), 2.43 (p, 2H, J=5.9 Hz), 1.1-0.9 (m, 4H), 0.2 (s, 18H). ¹³C-NMR: (CDCl₃, 100 MHz) δ 169.8, 168.3, 164.0, 162.7, 153.3, 152.6, 149.28, 149.0, 147.6, 139.6, 134.8, 134.5, 127.9, 127.5, 125.1, 123.21, 121.5, 120.5, 120.1, 116.4, 113.2, 108.7, 79.8, 79.6, 68.7, 68.5, 67.0, 66.8, 58.8, 58.0, 57.6, 32.8, 32.0, 30.3, 19.7, 0.25.

(b) (S)-2-(4-Aminophenyl)-8-(3-(((S)-2-cyclopropyl-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-10-((2-(trimethylsilyl)ethoxy)methyl)-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-5,11(10H,11aH)-dione (14)

Triphenylarsine (0.24 g, 0.8 mmol), silver (I) oxide (1.02 g, 4.4 mmol), cyclopropylboronic acid (0.47 g, 5.5 mmol) and starting material 13 (1.15 g, 1.1 mmol) were dissolved in dioxane (30 mL) under an argon atmosphere. Potassium phosphate tribasic (2.8 g, 13.2 mmol) was ground-up with a pestle and mortar and quickly added to the reaction mixture. The reaction mixture was evacuated and flushed with argon 3 times and heated to 71° C. Palladium (II) bis(benzonitrile chloride) (84 mg, 0.22 mmol) was added and the reaction vessel was evacuated and flushed with argon 3 times. After 10 minutes a small sample was taken for analysis by TLC (80:20 v/v ethyl acetate/hexane) and LC/MS. After 30 minutes the reaction had gone to completion (LC/MS analysis indicated complete consumption of starting material) and the reaction was filtered through celite and the filter pad washed with ethyl acetate (400 mL). The filtrate was washed with water (2×200 mL) and brine (2×200 mL). The organic layer was dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (30:70 v/v Hexane/Ethyl acetate) afforded the product 14 as an orangey/yellow solid (0.66 g, 63%). Method 1, LC/MS (3.85 min (ES⁺) m/z (relative intensity) 952.17 ([M+H]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ 7.36 (d, 2H, J=8.4 Hz), 7.30 (s, 1H), 7.25-7.19 (m, 4H), 6.68 (s, 1H), 6.62 (d, 2H, J=8.4 Hz), 5.49 (dd, 2H, J=5.6, 10.0 Hz), 4.73 (app. t, 2H, J=10.8 Hz), 4.54 (dd, 1H, J=3.2, 10.4 Hz), 4.40 (dd, 1H, J=3.2, 10.4 Hz), 4.29-4.23 (m, 4H), 3.91-3.85 (m, 7H), 3.80-3.71 (m, 2H), 3.70-3.61 (m, 2H), 3.38-3.32 (m, 1H), 3.12-3.01 (m, 1H), 2.50-2.69 (m, 1H), 2.40 (q, 2H, J=5.6 Hz), 1.50-1.43 (m, 1H), 0.99-0.71 (m, 6H), 0.54-0.59 (m, 2H), 0.00 (s, 18H) ppm.

(c) (S)-2-(4-Aminophenyl)-8-(3-(((S)-2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-5(11aH)-one (15)

SEM dilactam 14 (0.66 g, 0.69 mmol) was dissolved in THF (23 mL) and cooled to −78° C. under an argon atmosphere. Super-Hydride® solution (1.7 mL, 1 M in THF) was added drop wise over 5 minutes while monitoring the temperature. After 20 minutes a small sample was taken and washed with water for LC/MS analysis. Water (50 mL) was added and the cold bath was removed. The organic layer was extracted and washed with brine (60 mL). The combined aqueous layers were washed with CH₂Cl₂/MeOH (90/10 v/v) (2×50 mL). The combined organic layers were dried with MgSO₄, filtered and the solvent removed in vacuo. The crude product was dissolved in MeOH (48 mL), CH₂Cl₂ (18 mL) and water (6 mL) and sufficient silica gel was added to afford a thick suspension. After 5 days stirring, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (˜200 mL) until product ceased to be eluted. The organic layer was washed with brine (2×70 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (100% CHCl₃ to 96/4 v/v CHCl₃/MeOH) afforded the product 15 as a yellow solid (302 mg, 66%). Method 1, LC/MS (2.42 min (ES⁺) m/z (relative intensity) 660.74 ([M+H]⁺, 30). ¹H NMR (400 MHz, CDCl₃) δ 7.86 (d, 1H, J=3.6 Hz), 7.78 (d, 1H, J=3.6 Hz), 7.58-7.44 (m, 3H), 7.34-7.20 (m, 3H), 6.88-6.66 (m, 4H), 4.35-4.15 (m, 6H), 3.95-3.75 (m, 7H), 3.39-3.22 (m, 1H), 3.14-3.04 (m, 1H), 2.93-2.85 (m, 1H), 2.46-2.36 (m, 2H), 1.49-1.41 (m, 1H), 0.80-0.72 (m, 2H), 0.58-0.51 (app. s, 2H) ppm.

(d) Allyl ((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (16)

In a degassed round bottom flask filled with argon, HO-Ala-Val-alloc (149.6 mg, 0.549 mmol) and EEDQ (135.8 mg, 0.549 mmol) were dissolved in a 9:1 mixture of dry CH₂Cl₂/MeOH (5 mL). The flask was wrapped in aluminium foil and the reaction mixture was allowed to stir at room temperature for 1 hour before starting material 15 (302 mg, 0.457 mmol) was added. The reaction mixture was left to stir for a further 40 hours at room temperature before the volatiles were removed by rotary evaporation under reduced pressure (the reaction was followed by LC/MS, RT starting material 2.32 min, (ES⁺660.29 ([M+H]⁺, 100)). The crude product was directly purified by silica gel chromatography column (100% CHCl₃ to 90/10 v/v CHCl₃/MeOH) to afford the pure product (16) in 42% yield (174 mg). Method 2 LC/MS (2.70 min (ES+) m/z (relative intensity) 914.73 ([M+H]⁺, 60), 660.43 (60), 184.31 (100)).

(e) (2S)-2-amino-N-((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (17)

The starting material 16 (170 mg, 0.185 mmol) was dissolved in dry CH₂Cl₂ (5 mL) in a round bottom flask filled with argon, before pyrrolidine (41 μL, 0.21 mmol) was added. The flask was purged/refilled three times with argon before Pd(PPh₃)₄ (14 mg, 0.084 mmol) was added and the flushing operation repeated. After 1 hour, complete consumption of starting material was observed (the reaction was followed by LC/MS) and Et₂O (50 mL) was added to the reaction mixture which was allowed to stir until all the product had crashed out of solution. The solid was filtered through a sintered funnel and washed twice with Et₂O (2×25 mL). The collecting flask was replaced and the isolated solid was dissolved in CHCl₃ (100 mL or until all the product had passed through the sintered funnel). The volatiles were then removed by rotary evaporation under reduced pressure to afford the crude product 17 which was used directly in the next step (168 mg). LC/MS method 2 (2.70 min (ES+) m/z (relative intensity) 830.27 ([M+H]⁺, 50), 660.13 (80), 171.15 (100)).

(f) N—((R)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12,15, 18,21,24-octaoxaheptacosan-27-amide (18)

Starting material 17 (154 mg, 0.185 mmol) and EDCl.HCl (110 mg, 0.185 mmol) were solubilised in dry CH₂Cl₂ (5 mL) in a round bottom flask purged and filled with argon. The mixture was left to stir at room temperature for 1 hour before PEG₈-maleimide (35.6 mg, 0.185 mmol) was added and the reaction mixture stirred for a further 16 hours (or until the reaction is complete, monitored by LC/MS). The reaction solution was diluted with CH₂Cl₂ (50 mL) and the organics were washed with H₂O (50 mL) and brine (50 mL) before being dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure to afford the crude product. Purification on silica gel column chromatography (100% CHCl₃ to 85/15 v/v CHCl₃/MeOH) gave the desired product (135 mg), however remaining traces of unreacted PEG₈-maleimide were observed (by LC/MS, 2.21 min, method 2). Automated reverse phase silica gel chromatography (H₂O/CH₃CN) (see general information for conditions) successfully removed the impurity affording pure final product (18, 37 mg of pure product starting from 110 mg, 33%). Overall yield=17%. Method 2 LC/MS (2.58 min (ES+) m/z (relative intensity) 1404.03 ([M+H]⁺, 20), 702.63 (100)). ¹H NMR (400 MHz, CDCl₃) δ 7.91 (t, J=3.5 Hz, 1H), 7.80 (d, J=4.0 Hz, 1H), 7.75 (d, J=8.8 Hz, 1H), 7.69 (d, J=8.7 Hz, 1H), 7.54-7.50 (m, 2H), 7.45 (s, 1H), 7.39-7.31 (m, 2H), 6.87 (d, J=10.5 Hz, 2H), 6.76 (s, 1H), 6.72-6.68 (m, 2H), 4.74-4.62 (m, 1H), 4.45-4.17 (m, 7H), 3.95 (s, 3H), 3.94 (s, 3H), 3.67-3.58 (m, 34H), 3.54 (m, 2H), 3.42 (dd, J=10.2, 5.2 Hz, 2H), 3.16-3.07 (m, 1H), 2.92 (dd, J=16.1, 4.1 Hz, 1H), 2.62-2.49 (m, 4H), 2.48-2.39 (m, 2H), 2.37-2.25 (m, 1H), 1.92 (s, 1H), 1.52-1.44 (m, 3H), 1.10-0.93 (m, 6H), 0.79 (dd, J=9.2, 5.3 Hz, 2H), 0.57 (dd, J=9.2, 5.3 Hz, 2H), NH were not observed.

Example 2

(a) (R)-2-((R)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido) Propanoic Acid (20b)

HO-Ala-Val-H 20a (350 mg, 1.86 mmol) and Na₂CO₃ (493 mg, 4.65 mmol) were dissolved in distilled H₂O (15 mL) and the mixture was cooled to 0° C. before dioxane (15 mL) was added (partial precipitation of the amino acid salt occurred). A solution of Fmoc-Cl (504 mg, 1.95 mmol) in dioxane (15 mL) was added dropwise with vigorous stirring over 10 minutes. The resulting mixture was stirred at 0° C. for 2 hours before the ice bath was removed and stirring was maintained for 16 hours. The solvent was removed by rotary evaporation under reduced pressure and the residue dissolved in water (150 mL). The pH was adjusted from 9 to 2 with 1N HCl and the aqueous layer was subsequently extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure to afford pure HO-Ala-Val-Fmoc 20b (746 mg, 97% yield). LC/MS 2.85 min (ES+) m/z (relative intensity) 410.60; ¹H-NMR (400 MHz, CDCl₃) δ 7.79 (d, J=7.77 Hz, 2H), 7.60 (d, J=7.77 Hz, 2H), 7.43 (d, J=7.5 Hz, 2H), 7.34 (d, J=7.5 Hz, 2H), 6.30 (bs, 1H), 5.30 (bs, 1H), 4.71-7.56 (m, 1H), 4.54-4.36 (m, 2H), 4.08-3.91 (m, 1H), 2.21-2.07 (m, 1H), 1.50 (d, J=7.1 Hz, 3H), 1.06-0.90 (m, 6H).

(b) (9H-fluoren-9-yl)methyl((S)-3-methyl-1-oxo-1-(((S)-1-oxo-1-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)amino)propan-2-yl)amino)butan-2-yl)carbamate (20)

4-Aminophenylboronic acid pinacol ester was added (146.9 mg, 0.67 mmol) was added to a solution of HO-Ala-Val-Fmoc 20b (330 mg, 0.8 mmol), DCC (166 mg, 0.8 mmol) and DMAP (5 mg, cat.) in dry DCM (8 mL) previously stirred for 30 minutes at room temperature in a flask flushed with argon. The reaction mixture was then allowed to stir at room temperature overnight. The reaction was followed by LCMS and TLC. The reaction mixture was diluted with CH₂Cl₂ and the organics were washed with H₂O and brine before being dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dryloaded on a silicagel chromatography column (Hexane/EtOAc, 6:4) and pure product 20 was isolated as a white solid in 88% yield (360 mg).

(c) 8-(3-((2-(4-((S)-2-((S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido)propanamido)phenyl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl trifluoromethanesulfonate (21)

Bis-triflate 12 (2.03 g, 1.81 mmol), boronic pinacol ester (1 g, 1.63 mmol) and Na₂CO₃ (881 mg, 8.31 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (40 mL). The reaction flask was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (41 mg, 0.035 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduce pressure and the residue was taken up in H₂O (100 mL) and extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (Hexane/EtOAc, 8:2 to 25:75) to afford pure 21 in 33% yield (885 mg). LC/MS 3.85 min (ES+) m/z (relative intensity) 1452.90; ¹H NMR (400 MHz, CDCl₃) δ 7.78-7.16 (m, 17H), 7.13 (s, 1H), 6.51-6.24 (m, 1H), 5.51 (dd, J=10.0, 5.1 Hz, 2H), 5.36-5.11 (m, 1H), 4.74 (dd, J=10.1, 4.4 Hz, 2H), 4.70-4.53 (m, 2H), 4.47 (d, J=6.4 Hz, 1H), 4.37 (d, J=7.2 Hz, 1H), 4.27 (m, 4H), 4.20-4.14 (m, 1H), 3.90 (s, 3H), 3.89 (s, 3H), 3.77 (ddd, J=16.7, 9.0, 6.4 Hz, 3H), 3.71-3.61 (m, 2H), 3.24-2.91 (m, 3H), 2.55-2.33 (m, 2H), 2.22-2.07 (m, 1H), 1.52-1.37 (m, 3H), 1.04-0.86 (m, 10H), 0.00 (s, 18H).

(d) (9H-fluoren-9-yl)methyl((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl) Carbamate (22)

Triphenylarsine (42 mg, 0.137 mmol) was added to a mixture of PBD-triflate 21 (250 mg, 0.172 mmol), cyclopropylboronic acid (73.9 mg, 0.86 mmol), silver oxide (159 mg, 0.688 mmol) and potassium phosphate tribasic (438 mg, 2.06 mmol) in dry dioxane (10 mL) under an argon atmosphere. The reaction was flushed with argon 3 times and bis(benzonitrile)palladium(II) chloride (13.2 mg, 0.034 mmol) was added. The reaction was flushed with Argon 3 more times before being warmed to 75° C. and stirred for 10 minutes. The reaction mixture was filtered through a pad of celite which was subsequently rinsed with ethyl acetate. The solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 1% methanol/chloroform). Pure fractions were collected and combined, and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 22 (132 mg, 50% yield). LC/MS 3.83 min (ES+) m/z (relative intensity) 1345.91; ¹H NMR (400 MHz, CDCl₃) δ 7.88-7.14 (m, 17H), 6.69 (s, 1H), 6.45-6.25 (m, 1H), 5.57-5.41 (m, 2H), 5.34-5.14 (m, 1H), 4.78-4.67 (m, 2H), 4.62-4.55 (m, 1H), 4.50-4.45 (m, 2H), 4.51-4.44 (m, 1H), 4.31-4.21 (m, 4H), 4.16 (m, 1H), 3.92 (s, 3H), 3.86 (s, 3H), 3.82-3.71 (m, 2H), 3.66 (m, 3H), 3.40-3.28 (m, 1H), 3.07 (m, 1H), 2.70-2.57 (m, 1H), 2.47-2.36 (m, 2H), 2.15 (m, 1H), 1.51-1.40 (m, 3H), 1.03-0.87 (m, 11H), 0.77-0.71 (m, 2H), 0.60-0.54 (m, 2H), 0.00 (t, J=3.0 Hz, 18H).

(e) (9H-fluoren-9-yl)methyl((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (23)

A solution of Super-Hydride® (0.5 mL, 1M in THF) was added dropwise to a solution of SEM dilactam 22 (265 mg g, 0.19 mmol) in THF (10 mL) at −78° C. under an argon atmosphere. The addition was completed over 5 minutes in order to maintain the internal temperature of the reaction mixture constant. After 20 minutes, an aliquot was quenched with water for LC/MS analysis, which revealed that the reaction was complete. Water (20 mL) was added to the reaction mixture and the cold bath was removed. The organic layer was extracted with EtOAc (3×30 mL) and the combined organics were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dissolved in MeOH (12 mL), CH₂Cl₂ (6 mL), water (2 mL) and enough silica gel to form a thick stirring suspension. After 5 days, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (200 mL) until the elution of the product was complete. The organic layer was washed with brine (2×70 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. Purification by silica gel column chromatography (100% CHCl₃ to 96% CHCl₃/4% MeOH) afforded the product 23 as a yellow solid (162 mg, 78%). LC/MS 3.02 min (ES+) m/z (relative intensity) 1052.37.

(f) (2S)-2-amino-N-((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (17)

Excess piperidine was added (0.2 mL, 2 mmol) to a solution of SEM-dilactam 23 (76 mg, 0.073 mmol) in DMF (1 mL). The mixture was allowed to stir at room temperature for 20 min, at which point the reaction had gone to completion (as monitored by LC/MS). The reaction mixture was diluted with CH₂Cl₂ (75 mL) and the organic phase was washed with H₂O (3×75 mL) until complete piperidine removal. The organic phase was dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford crude product 17 which was used as such in the next step. LC/MS 2.32 min (ES+) m/z (relative intensity) 830.00.

(g) N-((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (18)

EDCl hydrochloride (14 mg, 0.0732 mmol) was added to a suspension of Maleimide-PEG₈-acid (43.4 mg, 0.0732 mmol) in dry CH₂Cl₂ (5 mL) under argon atmosphere. The mixture was stirred for 1 hour at room temperature before PBD 17 (60.7 mg, 0.0732 mmol) was added. Stirring was maintained until the reaction was complete (usually 5 hours). The reaction was diluted with CH₂Cl₂ and the organic phase was washed with H₂O and brine before being dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure by rotary evaporation under reduced pressure. The product was purified by careful silica gel chromatography (slow elution starting with 100% CHCl₃ up to 9:1 CHCl₃/MeOH) followed by reverse phase chromatography to remove unreacted maleimide-PEG₈-acid. The product 18 was isolated in 17.6% (21.8 mg). LC/MS 2.57 min (ES+) m/z (relative intensity) 1405.30; ¹H NMR (400 MHz, CDCl₃) δ 7.91 (t, J=3.5 Hz, 1H), 7.80 (d, J=4.0 Hz, 1H), 7.75 (d, J=8.8 Hz, 1H), 7.69 (d, J=8.7 Hz, 1H), 7.54-7.50 (m, 2H), 7.45 (s, 1H), 7.39-7.31 (m, 2H), 6.87 (d, J=10.5 Hz, 2H), 6.76 (s, 1H), 6.72-6.68 (m, 2H), 4.74-4.62 (m, 1H), 4.45-4.17 (m, 7H), 3.95 (s, 3H), 3.94 (s, 3H), 3.67-3.58 (m, 34H), 3.54 (m, 2H), 3.42 (dd, J=10.2, 5.2 Hz, 2H), 3.16-3.07 (m, 1H), 2.92 (dd, J=16.1, 4.1 Hz, 1H), 2.62-2.49 (m, 4H), 2.48-2.39 (m, 2H), 2.37-2.25 (m, 1H), 1.92 (s, 1H), 1.52-1.44 (m, 3H), 1.10-0.93 (m, 6H), 0.79 (dd, J=9.2, 5.3 Hz, 2H), 0.57 (dd, J=9.2, 5.3 Hz, 2H), NH were not observed.

Example 3

(S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl trifluoromethanesulfonate (24)

Pd(PPh₃)₄ (20.6 mg, 0.018 mmol) was added to a stirred mixture of the bis-enol triflate 12 (500 mg, 0.44 mmol), N-methyl piperazine boronic ester (100 mg, 0.4 mmol), Na₂CO₃ (218 mg, 2.05 mmol), MeOH (2.5 mL), toluene (5 mL) and water (2.5 mL). The reaction mixture was allowed to stir at 30° C. under a nitrogen atmosphere for 24 hours after which time all the boronic ester has consumed. The reaction mixture was then evaporated to dryness before the residue was taken up in EtOAc (100 mL) and washed with H₂O (2×50 mL), brine (50 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 80:20 v/v Hexane/EtOAc to 60:40 v/v Hexane/EtOAc) afforded product 24 as a yellowish foam (122.6 mg, 25%). LC/MS 3.15 min (ES+) m/z (relative intensity) 1144 ([M+H]⁺, 20%).

(b) (9H-fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl) Carbamate (25)

PBD-triflate 24 (359 mg, 0.314 mmol), boronic pinacol ester 20 (250 mg, 0.408 mmol) and triethylamine (0.35 mL, 2.51 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (3 mL). The microwave vessel was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (21.7 mg, 0.018 mmol) was added and the reaction mixture placed in the microwave at 80° C. for 10 minutes. Subsequently, CH₂Cl₂ (100 mL) was added and the organics were washed with water (2×50 mL) and brine (50 mL) before being dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (CHCl₃/MeOH, 100% to 9:1) to afford pure 25 (200 mg, 43% yield). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]⁺, 100%).

(c) (9H-fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (26)

A solution of Super-Hydride® (0.34 mL, 1M in THF) was added dropwise to a solution of SEM-dilactam 25 (200 mg, 0.135 mmol) in THF (5 mL) at −78° C. under an argon atmosphere. The addition was completed over 5 minutes in order to maintain the internal temperature of the reaction mixture constant. After 20 minutes, an aliquot was quenched with water for LC/MS analysis, which revealed that the reaction was complete. Water (20 mL) was added to the reaction mixture and the cold bath was removed. The organic layer was extracted with EtOAc (3×30 mL) and the combined organics were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dissolved in MeOH (6 mL), CH₂Cl₂ (3 mL), water (1 mL) and enough silica gel to form a thick stirring suspension. After 5 days, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until the elution of the product was complete. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. Purification by silica gel column chromatography (100% CHCl₃ to 96% CHCl₃/4% MeOH) afforded the product 26 as a yellow solid (100 mg, 63%). LC/MS 2.67 min (ES+) m/z (relative intensity) 1186 ([M+H]⁺, 5%).

(d) (S)-2-amino-N—((S)-1-((4-((R)-7-methoxy-8-(3-(((R)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (27)

Excess piperidine was added (0.1 mL, 1 mmol) to a solution of PBD 26 (36.4 mg, 0.03 mmol) in DMF (0.9 mL). The mixture was allowed to stir at room temperature for 20 min, at which point the reaction had gone to completion (as monitored by LC/MS). The reaction mixture was diluted with CH₂Cl₂ (50 mL) and the organic phase was washed with H₂O (3×50 mL) until complete piperidine removal. The organic phase was dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford crude product 27 which was used as such in the next step. LC/MS 2.20 min (ES+) m/z (relative intensity) 964 ([M+H]⁺, 5%).

(e) 6-(2,5-dioxo-2,5-dihydro 1H-pyrrol-1-yl)-N—((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)hexanamide (28)

EDCl hydrochloride (4.7 mg, 0.03 mmol) was added to a suspension of 6-maleimidohexanoic acid (6.5 mg, 0.03 mmol) in dry CH₂Cl₂ (3 mL) under argon atmosphere. The mixture was stirred for 1 hour at room temperature before PBD 27 (34 mg, crude) was added. Stirring was maintained until the reaction was complete (6 hours). The reaction was diluted with CH₂Cl₂ and the organic phase was washed with H₂O and brine before being dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure by rotary evaporation under reduced pressure. The product was purified by careful silica gel chromatography (slow elution starting with 100% CHCl₃ up to 9:1 CHCl₃/MeOH) followed by reverse phase chromatography to remove unreacted maleimide-PEG₈-acid. The product 28 was isolated in 41% over two steps (14.6 mg). LC/MS 2.40 min (ES+) m/z (relative intensity) 1157 ([M+H]⁺, 5%)

Example 4—Alternative Synthesis of Compound 25

PBD-triflate 21 (469 mg, 0.323 mmol), boronic pinacol ester (146.5 mg, 0.484 mmol) and Na₂CO₃ (157 mg, 1.48 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (10 mL). The reaction flask was purged with argon three times before tetrakis(triphenylphosphine)palladium(0) (7.41 mg, 0.0064 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduced pressure and the residue was taken up in H₂O (50 mL) and extracted with EtOAc (3×50 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (CHCl₃ 100% to CHCl₃/MeOH 95%:5%) to afford pure 25 in 33% yield (885 mg). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]⁺, 100%).

Example 5

(S)-2-(4-Aminophenyl)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxymethyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxypropoxy-7-methoxy-10-((2-(trimethylsilyl)ethoxymethyl)-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H,11aH)-dione (29)

3,4-(Methylenedioxy)phenyl boronic acid (356 mg, 2.1 mmol, 1.3 equiv.), TEA (1.8 mL, 12.9 mmol, 8 equiv.) and triflate/aniline 13 (1.75 g, 1.7 mmol, 1 equiv.) were dissolved in a mixture of ethanol (7 mL), toluene (13 mL) and water (2 mL) under an Ar atmosphere. The reaction mixture was evacuated and flushed with Ar 3 times, before addition of tetrakis(triphenylphosphine)palladium(0) (114 mg, 0.1 mmol, 0.06 equiv.). The flask was again evacuated and flushed with Ar 3 times and heated in a microwave at 80° C. for 8 minutes with 30 seconds pre-stirring time. Analysis by TLC (80:20 v/v ethyl acetate/hexane) indicated complete consumption of starting material. The reaction mixture was diluted with dichloromethane (50 mL) and washed with water (50 mL). The organic layer was dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (60:40 to 20:80 v/v hexane/ethyl acetate) afforded the product 29 as a yellow solid (1.21 g, 71%). LC/MS (3.92 min (ES⁺) m/z (relative intensity) 1032.44 ([M+H]⁺, 100).

(b) (S)-2-(4-Aminophenyl)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-1H-pyrrolo[2,1-c][1,4]benzodiazepin-5(11aH)-one (30)

SEM dilactam 29 (0.25 g, 0.24 mmol, 1 equiv.) was dissolved in THF (8 mL) and cooled to −78° C. under an Ar atmosphere. Super-Hydride® (0.6 mL, 1 M in THF, 2.5 equiv.) was added drop wise over 5 minutes while monitoring the temperature. After 20 minutes a small sample was taken and worked-up for LCMS analysis. Water (50 mL) was added, the cold bath was removed and the solution washed with ethyl acetate (50 mL). The organic layer was extracted and washed with brine (60 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. The crude product was dissolved in EtOH (15 mL), CH₂Cl₂ (7.5 mL) and water (2.5 mL) and enough silica gel was added until it was a thick suspension. After 5 days stirring, it was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until product ceased to be eluted. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (CHCl₃ with 1% to 4% MeOH gradient) afforded the product 30 as a yellow solid (94 mg, 53%). LC/MS (2.53 min (ES⁺) m/z (relative intensity) 739.64 ([M]⁺, 70).

(c) Allyl((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (31)

Under an Ar atmosphere, Alanine-Valine-Alloc (180 mg, 0.66 mmol, 1.2 equiv.) was stirred with EEDQ (163 mg, 0.66 mmol, 1.2 equiv.) in anhydrous CH₂Cl₂ (21 mL) and methanol (1 mL) for 1 hour. The PBD 30 (407 mg, 0.55 mmol, 1 equiv.) was dissolved in anhydrous CH₂Cl₂ (21 mL) and methanol (1 mL) and added to the reaction. LC/MS after 5 days stirring at room temperature showed majority product formation. The solvent was removed in vacuo before purification by column chromatography (CH₂Cl₂ with 1% to 6% MeOH gradient) to yield the product 31 as a yellow solid (184 mg, 34%). LC/MS (2.95 min (ES⁺) m/z (relative intensity) 994.95 ([M+H]⁺, 60).

(d) (S)-2-Amino-N—((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (32)

The imine 31 (100 mg, 0.1 mmol, 1 equiv.) was dissolved in anhydrous DCM (10 mL) (with the aid of one drop of methanol to aid dissolution) under an Ar atmosphere. Pyrrolidine (30 μL, 0.15 mmol, 1.5 equiv.) was added drop wise before the flask was evacuated and flushed with Ar three times. Pd(PPh₃)₄ (7 mg, 6 μmol, 0.06 equiv.) was added and the flask was evacuated and flushed with Ar three times. LC/MS analysis after 1 hour indicated product formation and complete loss of starting material. Et₂O (60 mL) was added to the reaction mixture and it was left to stir until all the product had crashed out of solution. The precipitate was filtered through a sintered funnel and washed twice with Et₂O (2×20 mL). The collection flask was replaced and the isolated solid was dissolved and washed through the sinter with CHCl₃ (100 mL). The solvent was removed in vacuo to afford the crude product 32 as a yellow solid which was used directly in the next step. LC/MS (1.14 min (ES⁺) m/z (relative intensity) 910.40 ([M+H]⁺, 67).

(e) N—((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(Benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (33)

The imine 32 (92 mg, 0.1 mmol, 1.1 equiv.) was dissolved in CHCl₃ (6 mL) with one drop of anhydrous MeOH to aid dissolution. Maleimide-PEG₈-acid (53 mg, 0.09 mmol, 1 equiv.) was added followed by EEDQ (33 mg, 0.14 mmol, 1.5 equiv.). This was left to stir vigorously at room temperature under Ar for 4 days until LC/MS analysis showed majority product formation. The solvent was removed in vacuo and the crude product was partially purified by silica gel column chromatography (CHCl3 with 1% to 10% MeOH gradient) yielding 33 (81 mg). The material was purified further by preparative HPLC to give 33 as a yellow solid (26.3 mg, 18%). Fast Formic run: LC/MS (1.39 min (ES+) m/z (relative intensity) 1485.00 ([M+H]+, 64).

Example 6

(a) 9H-Fluoren-9-yl)methy ((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (34)

The triflate 21 (0.5 g, 0.35 mmol, 1 equiv.), 3,4-(methylenedioxy)phenyl boronic acid (75 mg, 0.45 mmol, 1.3 equiv.) and Na₂CO₃ (0.17 g, 1.6 mmol, 4.5 equiv.) were dissolved in toluene (11 mL), EtOH (5.5 mL) and water (5.5 mL) under an Ar atmosphere. The flask was evacuated and flushed with Ar three times. Pd(PPh₃)₄ (24 mg, 0.02 mmol, 0.06 equiv.) was added and again the flask was evacuated and flushed with Ar three times. This was heated to 30° C. and left stirring overnight. Analysis by LC/MS showed complete loss of starting material. The solvent was removed in vacuo and the residue dissolved in water (60 mL) before washing with ethyl acetate (60 mL×3). The combined organic layers were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by column chromatography (50:50 to 25:75 v/v hexane/ethyl acetate) afforded the product 34 as a yellow solid (310 mg, 64%). LC/MS (1.44 min (ES⁻) m/z (relative intensity) 1423.35 ([M−H]⁻, 79).

(b) (9H-Fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (35)

SEM dilactam 34 (0.31 g, 0.22 mmol, 1 equiv.) was dissolved in THF (10 mL) and cooled to −78° C. under an Ar atmosphere. Super-Hydride® (0.5 mL, 1 M in THF, 2.5 equiv.) was added drop wise over 5 minutes while monitoring the temperature. After 30 minutes a small sample was taken and worked-up for LC/MS analysis. Water (50 mL) was added, the cold bath was removed and the solution washed with ethyl acetate (50 mL). The organic layer was extracted and washed with brine (60 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. The crude product was dissolved in EtOH (13.2 mL), CH₂Cl₂ (6.6 mL) and water (2.2 mL) and enough silica gel was added until it was a thick suspension. After 5 days stirring, it was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until product ceased to be eluted. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (CHCl₃ with 1% to 4% MeOH gradient) afforded the pure product 35 as a yellow solid (185 mg, 75%). LC/MS (1.70 min (ES⁺) m/z (relative intensity) 1132.85 ([M+H]⁺, 60).

(c) (S)-2-Amino-N—((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (32)

The imine 35 (82 mg, 0.07 mmol, 1 equiv.) was dissolved in DMF (1 mL) before piperidine (0.2 mL, 2 mmol, excess) was added slowly. This solution was left to stir at room temperature for 20 minutes until LC/MS analysis showed complete consumption of starting material. The reaction mixture was diluted with CH₂Cl₂ (50 mL), washed with water (50 mL×4), dried with MgSO₄, filtered and the solvent removed in vacuo. The product 33 was used without further purification in the next step. LC/MS (1.15 min (ES⁺) m/z (relative intensity) 910.60 ([M+H]⁺, 58).

Example 7 (i) (S)-(2-amino-5-methoxy-4-((triisopropylsilyl)oxy)phenyl)(2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl-methanone (49)

(a) 5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzaldehyde (42)

Neat triisopropylsilylchloride (56.4 mL, 262 mmol) was added to a mixture of imidazole (48.7 g, 715.23 mmol) and 4-hydroxy-5-methoxy-2-nitrobenzaldehyde 41 (47 g, 238 mmol) (ground together). The mixture was heated until the phenol and imidazole melted and went into solution (100° C.). The reaction mixture was allowed to stir for 15 minutes and was then allowed to cool, whereupon a solid was observed to form at the bottom of the flask (imidazole chloride). The reaction mixture was diluted with 5% EtOAc/hexanes and loaded directly onto silica gel and the pad was eluted with 5% EtOAc/hexanes, followed by 10% EtOAc/hexanes (due to the low excess, very little unreacted TIPSCl was found in the product). The desired product was eluted with 5% ethyl acetate in hexane. Excess eluent was removed by rotary evaporation under reduced pressure, followed by drying under high vacuum to afford a crystalline light sensitive solid (74.4 g, 88%). Purity satisfactory by LC/MS (4.22 min (ES+) m/z (relative intensity) 353.88 ([M+H]⁺, 100)); ¹H NMR (400 MHz, CDCl₃) δ 10.43 (s, 1H), 7.60 (s, 1H), 7.40 (s, 1H), 3.96 (s, 3H), 1.35-1.24 (m, 3H), 1.10 (m, 18H).

(b) 5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoic Acid (43)

A solution of sodium chlorite (47.3 g, 523 mmol, 80% technical grade) and sodium dihydrogenphosphate monobasic (35.2 g, 293 mmol) (NaH₂PO₄) in water (800 mL) was added to a solution of compound 2 (74 g, 209 mmol) in tetrahydrofuran (500 mL) at room temperature. Hydrogen peroxide (60% w/w, 140 mL, 2.93 mol) was immediately added to the vigorously stirred biphasic mixture. The reaction mixture evolved gas (oxygen), the starting material dissolved and the temperature of the reaction mixture rose to 45° C. After 30 minutes LC/MS revealed that the reaction was complete. The reaction mixture was cooled in an ice bath and hydrochloric acid (1 M) was added to lower the pH to 3 (this step was found unnecessary in many instances, as the pH at the end of the reaction is already acidic; please check the pH before extraction). The reaction mixture was then extracted with ethyl acetate (1 L) and the organic phases washed with brine (2×100 mL) and dried over magnesium sulphate. The organic phase was filtered and excess solvent removed by rotary evaporation under reduced pressure to afford the product 43 in quantitative yield as a yellow solid. LC/MS (3.93 min (ES−) m/z (relative intensity) 367.74 ([M−H]⁻, 100)); ¹H NMR (400 MHz, CDCl₃) δ 7.36 (s, 1H), 7.24 (s, 1H), 3.93 (s, 3H), 1.34-1.22 (m, 3H), 1.10 (m, 18H).

(c) ((2S,4R)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-hydroxypyrrolidin-1-yl)(5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)phenyl)methanone (45)

DCC (29.2 g, 141 mmol, 1.2 eq) was added to a solution of acid 3 (43.5 g, 117.8 mmol, 1.1 eq), and hydroxybenzotriazole hydrate (19.8 g, 129.6 mmol, 1.1 eq) in dichloromethane (200 mL) at 0° C. The cold bath was removed and the reaction was allowed to proceed for 30 mins at room temperature, at which time a solution of (2S,4R)-2-t-butyldimethylsilyloxymethyl-4-hydroxypyrrolidine 44 (30 g, 129.6 mmol, 1.1 eq) and triethylamine (24.66 mL, 176 mmol, 1.5 eq) in dichloromethane (100 mL) was added rapidly at −10° C. under argon (on large scale, the addition time could be shortened by cooling the reaction mixture even further. The reaction mixture was allowed to stir at room temperature for 40 minutes to 1 hour and monitored by LC/MS and TLC (EtOAc). The solids were removed by filtration over celite and the organic phase was washed with cold aqueous 0.1 M HCl until the pH was measured at 4 or 5. The organic phase was then washed with water, followed by saturated aqueous sodium bicarbonate and brine. The organic layer was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure. The residue was subjected to column flash chromatography (silica gel; gradient 40/60 ethyl acetate/hexane to 80/20 ethyl acetate/hexane). Excess solvent was removed by rotary evaporation under reduced pressure afforded the pure product 45, (45.5 g of pure product 66%, and 17 g of slightly impure product, 90% in total). LC/MS 4.43 min (ES+) m/z (relative intensity) 582.92 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.66 (s, 1H), 6.74 (s, 1H), 4.54 (s, 1H), 4.40 (s, 1H), 4.13 (s, 1H), 3.86 (s, 3H), 3.77 (d, J=9.2 Hz, 1H), 3.36 (dd, J=11.3, 4.5 Hz, 1H), 3.14-3.02 (m, 1H), 2.38-2.28 (m, 1H), 2.10 (ddd, J=13.3, 8.4, 2.2 Hz, 1H), 1.36-1.19 (m, 3H), 1.15-1.05 (m, 18H), 0.91 (s, 9H), 0.17-0.05 (m, 6H), (presence of rotamers).

(d) (S)-5-(((tert-butyldimethylsilyl)oxy)methyl)-1-(5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoyl)pyrrolidin-3-one (46)

TCCA (8.82 g, 40 mmol, 0.7 eq) was added to a stirred solution of 45 (31.7 g, 54 mmol, 1 eq) and TEMPO (0.85 g, 5.4 mmol, 0.1 eq) in dry dichloromethane (250 mL) at 0° C. The reaction mixture was vigorously stirred for 20 minutes, at which point TLC (50/50 ethyl acetate/hexane) revealed complete consumption of the starting material. The reaction mixture was filtered through celite and the filtrate washed with aqueous saturated sodium bicarbonate (100 mL), sodium thiosulphate (9 g in 300 mL), brine (100 mL) and dried over magnesium sulphate. Rotary evaporation under reduced pressure afforded product 46 in quantitative yield. LC/MS 4.52 min (ES+) m/z (relative intensity) 581.08 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.78-7.60 (m, 1H), 6.85-6.62 (m, 1H), 4.94 (dd, J=30.8, 7.8 Hz, 1H), 4.50-4.16 (m, 1H), 3.99-3.82 (m, 3H), 3.80-3.34 (m, 3H), 2.92-2.17 (m, 2H), 1.40-1.18 (m, 3H), 1.11 (t, J=6.2 Hz, 18H), 0.97-0.75 (m, 9H), 0.15-−0.06 (m, 6H), (presence of rotamers).

(e) (S)-5-(((tert-butyldimethylsilyl)oxy)methyl)-1-(5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)benzoyl)-4,5-dihydro-1H-pyrrol-3-yl trifluoromethanesulfonate (47)

Triflic anhydride (27.7 mL, 46.4 g, 165 mmol, 3 eq) was injected (temperature controlled) to a vigorously stirred suspension of ketone 46 (31.9 g, 55 mmol, 1 eq) in dry dichloromethane (900 mL) in the presence of 2,6-lutidine (25.6 mL, 23.5 g, 220 mmol, 4 eq, dried over sieves) at −50° C. (acetone/dry ice bath). The reaction mixture was allowed to stir for 1.5 hours when LC/MS, following a mini work-up (water/dichloromethane), revealed the reaction to be complete. Water was added to the still cold reaction mixture and the organic layer was separated and washed with saturated sodium bicarbonate, brine and magnesium sulphate. The organic phase was filtered and excess solvent was removed by rotary evaporation under reduced pressure. The residue was subjected to column flash chromatography (silica gel; 10/90 v/v ethyl acetate/hexane), removal of excess eluent afforded the product 47 (37.6 g, 96%) LC/MS, method 2, 4.32 min (ES+) m/z (relative intensity) 712.89 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.71 (s, 1H), 6.75 (s, 1H), 6.05 (d, J=1.8 Hz, 1H), 4.78 (dd, J=9.8, 5.5 Hz, 1H), 4.15-3.75 (m, 5H), 3.17 (ddd, J=16.2, 10.4, 2.3 Hz, 1H), 2.99 (ddd, J=16.3, 4.0, 1.6 Hz, 1H), 1.45-1.19 (m, 3H), 1.15-1.08 (m, 18H), 1.05 (s, 6H), 0.95-0.87 (m, 9H), 0.15-0.08 (m, 6H).

(f) (S)-(2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl) (5-methoxy-2-nitro-4-((triisopropylsilyl)oxy)phenyl)methanone (48)

Triphenylarsine (1.71 g, 5.60 mmol, 0.4 eq) was added to a mixture of triflate 47 (10.00 g, 14 mmol, 1 eq), methylboronic acid (2.94 g, 49.1 mmol, 3.5 eq), silver oxide (13 g, 56 mmol, 4 eq) and potassium phosphate tribasic (17.8 g, 84 mmol, 6 eq) in dry dioxane (80 mL) under an argon atmosphere. The reaction was flushed with argon 3 times and bis(benzonitrile)palladium(II) chloride (540 mg, 1.40 mmol, 0.1 eq) was added. The reaction was flushed with argon 3 more times before being warmed instantaneously to 110° C. (the drysyn heating block was previously warmed to 110° C. prior addition of the flask). After 10 mins the reaction was cooled to room temperature and filtered through a pad celite. The solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; 10% ethyl acetate/hexane). Pure fractions were collected and combined, and excess eluent was removed by rotary evaporation under reduced pressure afforded the product 48 (4.5 g, 55%). LC/MS, 4.27 min (ES+) m/z (relative intensity) 579.18 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.70 (s, 1H), 6.77 (s, 1H), 5.51 (d, J=1.7 Hz, 1H), 4.77-4.59 (m, 1H), 3.89 (s, 3H), 2.92-2.65 (m, 1H), 2.55 (d, J=14.8 Hz, 1H), 1.62 (d, J=1.1 Hz, 3H), 1.40-1.18 (m, 3H), 1.11 (s, 9H), 1.10 (s, 9H), 0.90 (s, 9H), 0.11 (d, J=2.3 Hz, 6H).

(g) (S)-(2-amino-5-methoxy-4-((triisopropylsilyl)oxy)phenyl) (2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrol-1-yl)methanone (49)

Zinc powder (28 g, 430 mmol, 37 eq) was added to a solution of compound 48 (6.7 g, 11.58 mmol) in 5% formic acid in ethanol v/v (70 mL) at around 15° C. The resulting exotherm was controlled using an ice bath to maintain the temperature of the reaction mixture below 30° C. After 30 minutes the reaction mixture was filtered through a pad of celite. The filtrate was diluted with ethyl acetate and the organic phase was washed with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 10% ethyl acetate in hexane). The pure fractions were collected and combined and excess solvent was removed by rotary evaporation under reduced pressure to afford the product 49 (5.1 g, 80%). LC/MS, 4.23 min (ES+) m/z (relative intensity) 550.21 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.28 (s, 1H), 6.67 (s, 1H), 6.19 (s, 1H), 4.64-4.53 (m, J=4.1 Hz, 1H), 4.17 (s, 1H), 3.87 (s, 1H), 3.77-3.69 (m, 1H), 3.66 (s, 3H), 2.71-2.60 (m, 1H), 2.53-2.43 (m, 1H), 2.04-1.97 (m, J=11.9 Hz, 1H), 1.62 (s, 3H), 1.26-1.13 (m, 3H), 1.08-0.99 (m, 18H), 0.82 (s, 9H), 0.03-−0.03 (m, J=6.2 Hz, 6H).

(ii) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-((5-iodopentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate

(a) (S)-allyl(2-(2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamate (50)

Allyl chloroformate (0.30 mL, 3.00 mmol, 1.1 eq) was added to a solution of amine 49 (1.5 g, 2.73 mmol) in the presence of dry pyridine (0.48 mL, 6.00 mmol, 2.2 eq) in dry dichloromethane (20 mL) at −78° C. (acetone/dry ice bath). After 30 minutes, the bath was removed and the reaction mixture was allowed to warm to room temperature. The reaction mixture was diluted with dichloromethane and saturated aqueous copper sulphate was added. The organic layer was then washed sequentially with saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford the product 50 which was used directly in the next reaction. LC/MS, 4.45 min (ES+) m/z (relative intensity) 632.91 ([M+H]⁺, 100)

(b) (S)-allyl(2-(2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamate (51)

The crude 50 was dissolved in a 7:1:1:2 mixture of acetic acid/methanol/tetrahydrofuran/water (28:4:4:8 mL) and allowed to stir at room temperature. After 3 hours, complete disappearance of starting material was observed by LC/MS. The reaction mixture was diluted with ethyl acetate and washed sequentially with water (2×500 mL), saturated aqueous sodium bicarbonate (200 mL) and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel, 25% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 51 (1 g, 71%). LC/MS, 3.70 min (ES+) m/z (relative intensity) 519.13 ([M+H]⁺, 95); ¹H NMR (400 MHz, CDCl₃) δ 8.34 (s, 1H), 7.69 (s, 1H), 6.78 (s, 1H), 6.15 (s, 1H), 5.95 (ddt, J=17.2, 10.5, 5.7 Hz, 1H), 5.33 (dq, J=17.2, 1.5 Hz, 1H), 5.23 (ddd, J=10.4, 2.6, 1.3 Hz, 1H), 4.73 (tt, J=7.8, 4.8 Hz, 1H), 4.63 (dt, J=5.7, 1.4 Hz, 2H), 4.54 (s, 1H), 3.89-3.70 (m, 5H), 2.87 (dd, J=16.5, 10.5 Hz, 1H), 2.19 (dd, J=16.8, 4.6 Hz, 1H), 1.70 (d, J=1.3 Hz, 3H), 1.38-1.23 (m, 3H), 1.12 (s, 10H), 1.10 (s, 8H).

(c) (11S,11aS)-allyl 11-hydroxy-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10 (5H)-carboxylate (52)

Dimethyl sulphoxide (0.35 mL, 4.83 mmol, 2.5 eq) was added dropwise to a solution of oxalyl chloride (0.2 mL, 2.32 mmol, 1.2 eq) in dry dichloromethane (10 mL) at −78° C. (dry ice/acetone bath) under an atmosphere of argon. After 10 minutes a solution of 51 (1 g, 1.93 mmol) in dry dichloromethane (8 mL) was added slowly with the temperature still at −78° C. After 15 min triethylamine (1.35 mL, dried over 4 Å molecular sieves, 9.65 mmol, 5 eq) was added dropwise and the dry ice/acetone bath was removed. The reaction mixture was allowed to reach room temperature and was extracted with cold hydrochloric acid (0.1 M), saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess dichloromethane was removed by rotary evaporation under reduced pressure to afford product 52 (658 mg, 66%). LC/MS, 3.52 min (ES+) m/z (relative intensity) 517.14 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.20 (s, 1H), 6.75-6.63 (m, J=8.8, 4.0 Hz, 2H), 5.89-5.64 (m, J=9.6, 4.1 Hz, 2H), 5.23-5.03 (m, 2H), 4.68-4.38 (m, 2H), 3.84 (s, 3H), 3.83-3.77 (m, 1H), 3.40 (s, 1H), 3.05-2.83 (m, 1H), 2.59 (d, J=17.1 Hz, 1H), 1.78 (d, J=1.3 Hz, 3H), 1.33-1.16 (m, 3H), 1.09 (d, J=2.2 Hz, 9H), 1.07 (d, J=2.1 Hz, 9H).

(d) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (53)

Tert-butyldimethylsilyltriflate (0.70 mL, 3.00 mmol, 3 eq) was added to a solution of compound 52 (520 mg, 1.00 mmol) and 2,6-lutidine (0.46 mL, 4.00 mmol, 4 eq) in dry dichloromethane (40 mL) at 0° C. under argon. After 10 min, the cold bath was removed and the reaction mixture was stirred at room temperature for 1 hour. The reaction mixture was extracted with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 10% ethyl acetate in hexane to 20% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 53 (540 mg, 85%). LC/MS, 4.42 min (ES+) m/z (relative intensity) 653.14 ([M+Na]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 7.20 (s, 1H), 6.71-6.64 (m, J=5.5 Hz, 2H), 5.83 (d, J=9.0 Hz, 1H), 5.80-5.68 (m, J=5.9 Hz, 1H), 5.14-5.06 (m, 2H), 4.58 (dd, J=13.2, 5.2 Hz, 1H), 4.36 (dd, J=13.3, 5.5 Hz, 1H), 3.84 (s, 3H), 3.71 (td, J=10.1, 3.8 Hz, 1H), 2.91 (dd, J=16.9, 10.3 Hz, 1H), 2.36 (d, J=16.8 Hz, 1H), 1.75 (s, 3H), 1.31-1.16 (m, 3H), 1.12-1.01 (m, J=7.4, 2.1 Hz, 18H), 0.89-0.81 (m, 9H), 0.25 (s, 3H), 0.19 (s, 3H).

(e) (11S,11aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10 (5H)-carboxylate (54)

Lithium acetate (87 mg, 0.85 mmol) was added to a solution of compound 53 (540 mg, 0.85 mmol) in wet dimethylformamide (6 mL, 50:1 DMF/water). After 4 hours, the reaction was complete and the reaction mixture was diluted with ethyl acetate (25 mL) and washed with aqueous citric acid solution (pH˜3), water and brine. The organic layer was dried over magnesium sulphate filtered and excess ethyl acetate was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 25% to 75% ethyl acetate in hexane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 54 (400 mg, quantitative). LC/MS, (3.33 min (ES+) m/z (relative intensity) 475.26 ([M+H]⁺, 100).

(f) (11S,1aS)-allyl 11-((tert-butyldimethylsilyl)oxy)-8-((5-iodopentyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (55)

Diiodopentane (0.63 mL, 4.21 mmol, 5 eq) and potassium carbonate (116 mg, 0.84 mmol, 1 eq) were added to a solution of phenol 54 (400 mg, 0.84 mmol) in acetone (4 mL, dried over molecular sieves). The reaction mixture was then warmed to 60° C. and stirred for 6 hours. Acetone was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 50/50, v/v, hexane/ethyl acetate). Pure fractions were collected and combined and excess eluent was removed to provide 55 in 90% yield. LC/MS, 3.90 min (ES+) m/z (relative intensity) 670.91 ([M]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ 7.23 (s, 1H), 6.69 (s, 1H), 6.60 (s, 1H), 5.87 (d, J=8.8 Hz, 1H), 5.83-5.68 (m, J=5.6 Hz, 1H), 5.15-5.01 (m, 2H), 4.67-4.58 (m, 1H), 4.45-4.35 (m, 1H), 4.04-3.93 (m, 2H), 3.91 (s, 3H), 3.73 (td, J=10.0, 3.8 Hz, 1H), 3.25-3.14 (m, J=8.5, 7.0 Hz, 2H), 2.92 (dd, J=16.8, 10.3 Hz, 1H), 2.38 (d, J=16.8 Hz, 1H), 1.95-1.81 (m, 4H), 1.77 (s, 3H), 1.64-1.49 (m, 2H), 0.88 (s, 9H), 0.25 (s, 3H), 0.23 (s, 3H).

(iii) (11S,11aS)-4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (70)

(a) Allyl 3-(2-(2-(4-((((2-((S)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl) carbamoyl)oxy)methyl)phenyl)hydrazinyl)propanamido)-4-methyl-2-oxopentanoate (56)

Triethylamine (2.23 mL, 18.04 mmol, 2.2 eq) was added to a stirred solution of the amine 49 (4 g, 8.20 mmol) and triphosgene (778 mg, 2.95 mmol, 0.36 eq) in dry tetrahydrofuran (40 mL) at 5° C. (ice bath). The progress of the isocyanate reaction was monitored by periodically removing aliquots from the reaction mixture and quenching with methanol and performing LC/MS analysis. Once the isocyanate formation was complete a solution of the alloc-Val-Ala-PABOH (4.12 g, 12.30 mmol, 1.5 eq) and triethylamine (1.52 mL, 12.30 mmol, 1.5 eq) in dry tetrahydrofuran (40 mL) was rapidly added by injection to the freshly prepared isocyanate. The reaction mixture was allowed to stir at 40° C. for 4 hours. Excess solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; gradient, 1% methanol to 5% methanol in dichloromethane). (Alternative chromatography conditions using EtOAc and Hexane have also been successful). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 56 (3.9 g, 50%). LC/MS, 4.23 min (ES+) m/z (relative intensity) 952.36 ([M+H]⁺, 100); ¹H NMR (400 MHz, CDCl₃) δ 8.62 (br s, 1H), 8.46 (s, 1H), 7.77 (br s, 1H), 7.53 (d, J=8.4 Hz, 2H), 7.32 (d, J=8.5 Hz, 2H), 6.76 (s, 1H), 6.57 (d, J=7.6 Hz, 1H), 6.17 (s, 1H), 6.03-5.83 (m, 1H), 5.26 (dd, J=33.8, 13.5 Hz, 3H), 5.10 (s, 2H), 4.70-4.60 (m, 2H), 4.58 (dd, J=5.7, 1.3 Hz, 2H), 4.06-3.99 (m, 1H), 3.92 (s, 1H), 3.82-3.71 (m, 1H), 3.75 (s, 3H), 2.79-2.64 (m, 1H), 2.54 (d, J=12.9 Hz, 1H), 2.16 (dq, J=13.5, 6.7 Hz, 1H), 1.67 (s, 3H), 1.46 (d, J=7.0 Hz, 3H), 1.35-1.24 (m, 3H), 1.12 (s, 9H), 1.10 (s, 9H), 0.97 (d, J=6.8 Hz, 3H), 0.94 (d, J=6.8 Hz, 3H), 0.87 (s, 9H), 0.07-−0.02 (m, 6H).

(b) Allyl 3-(2-(2-(4-((((2-((S)-2-(hydroxymethyl)-4-methyl-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl) carbamoyl)oxy)methyl)phenyl)hydrazinyl)propanamido)-4-methyl-2-oxopentanoate (57)

The TBS ether 56 (1.32 g, 1.38 mmol) was dissolved in a 7:1:1:2 mixture of acetic acid/methanol/tetrahydrofuran/water (14:2:2:4 mL) and allowed to stir at room temperature. After 3 hours no more starting material was observed by LC/MS. The reaction mixture was diluted with ethyl acetate (25 mL) and washed sequentially with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel, 2% methanol in dichloromethane). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 57 (920 mg, 80%). LC/MS, 3.60 min (ES+) m/z (relative intensity) 838.18 ([M+H]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ8.55 (s, 1H), 8.35 (s, 1H), 7.68 (s, 1H), 7.52 (d, J=8.1 Hz, 2H), 7.31 (d, J=8.4 Hz, 2H), 6.77 (s, 1H), 6.71 (d, J=7.5 Hz, 1H), 6.13 (s, 1H), 5.97-5.82 (m, J=5.7 Hz, 1H), 5.41-5.15 (m, 3H), 5.10 (d, J=3.5 Hz, 2H), 4.76-4.42 (m, 5H), 4.03 (t, J=6.6 Hz, 1H), 3.77 (s, 5H), 2.84 (dd, J=16.7, 10.4 Hz, 1H), 2.26-2.08 (m, 2H), 1.68 (s, 3H), 1.44 (d, J=7.0 Hz, 3H), 1.30 (dt, J=14.7, 7.4 Hz, 3H), 1.12 (s, 9H), 1.10 (s, 9H), 0.96 (d, J=6.8 Hz, 3H), 0.93 (d, J=6.8 Hz, 3H).

(c) (11S,11aS)-4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-hydroxy-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (58)

Dimethyl sulphoxide (0.2 mL, 2.75 mmol, 2.5 eq) was added dropwise to a solution of oxalyl chloride (0.11 mL, 1.32 mmol, 1.2 eq) in dry dichloromethane (7 mL) at −78° C. (dry ice/acetone bath) under an atmosphere of argon. After 10 minutes a solution of 57 (920 mg, 1.10 mmol) in dry dichloromethane (5 mL) was added slowly with the temperature still at −78° C. After 15 min triethylamine (0.77 mL, dried over 4 Å molecular sieves, 5.50 mmol, 5 eq) was added dropwise and the dry ice/acetone bath was removed. The reaction mixture was allowed to reach room temperature and was extracted with cold hydrochloric acid (0.1 M), saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess dichloromethane was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; gradient 2% methanol to 5% methanol in dichloromethane). Pure fractions were collected and combined and removal of excess eluent by rotary evaporation under reduced pressure afforded the product 58 (550 mg, 60%). LC/MS, 3.43 min (ES+) m/z (relative intensity) 836.01 ([M]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ 8.39 (s, 1H), 7.52-7.40 (m, 2H), 7.21-7.08 (m, J=11.5 Hz, 2H), 6.67 (s, 1H), 6.60-6.47 (m, J=7.4 Hz, 1H), 5.97-5.83 (m, 1H), 5.79-5.66 (m, 1H), 5.38-4.90 (m, 6H), 4.68-4.52 (m, J=18.4, 5.5 Hz, 4H), 4.04-3.94 (m, J=6.5 Hz, 1H), 3.87-3.76 (m, 5H), 3.00-2.88 (m, 1H), 2.66-2.49 (m, 2H), 2.21-2.08 (m, 2H), 1.76 (s, 3H), 1.45 (d, J=7.0 Hz, 3H), 1.09-0.98 (m, J=8.9 Hz, 18H), 0.96 (d, J=6.7 Hz, 3H), 0.93 (d, J=6.9 Hz, 3H).

(d) (11S,11aS)-4-(2-(1-((1-(Allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (59)

Tert-butyldimethylsilyltriflate (0.38 mL, 1.62 mmol, 3 eq) was added to a solution of compound 58 (450 mg, 0.54 mmol) and 2,6-lutidine (0.25 mL, 2.16 mmol, 4 eq) in dry dichloromethane (5 mL) at 0° C. under argon. After 10 min, the cold bath was removed and the reaction mixture was stirred at room temperature for 1 hour. The reaction mixture was extracted with water, saturated aqueous sodium bicarbonate and brine. The organic phase was dried over magnesium sulphate, filtered and excess solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; 50/50 v/v hexane/ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 59 (334 mg, 65%). LC/MS, 4.18 min (ES+) m/z (relative intensity) 950.50 ([M]⁺, 100). ¹H NMR (400 MHz, CDCl₃) δ 8.53 (s, 1H), 8.02 (s, 1H), 7.44 (d, J=7.6 Hz, 2H), 7.21 (s, 1H), 7.08 (d, J=8.2 Hz, 2H), 6.72-6.61 (m, J=8.9 Hz, 2H), 6.16 (s, 1H), 5.97-5.79 (m, J=24.4, 7.5 Hz, 2H), 5.41-5.08 (m, 5H), 4.86 (d, J=12.5 Hz, 1H), 4.69-4.60 (m, 1H), 4.57 (s, 1H), 4.03 (t, J=6.7 Hz, 1H), 3.87 (s, 3H), 3.74 (td, J=9.6, 3.6 Hz, 1H), 2.43-2.09 (m, J=34.8, 19.4, 11.7 Hz, 3H), 1.76 (s, 3H), 1.43 (d, J=6.9 Hz, 3H), 1.30-1.21 (m, 3H), 0.97 (d, J=6.7 Hz, 3H), 0.92 (t, J=8.4 Hz, 3H), 0.84 (s, 9H), 0.23 (s, 3H), 0.12 (s, 3H).

(e) (11S,11aS)-4-(2-(1-((1-(Allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-((tert-butyldimethylsilyl)oxy)-8-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-O(5H)-carboxylate (60)

Lithium acetate (50 mg, 0.49 mmol) was added to a solution of compound 59 (470 mg, 0.49 mmol) in wet dimethylformamide (4 mL, 50:1 DMF/water). After 4 hours, the reaction was complete and the reaction mixture was diluted with ethyl acetate and washed with citric acid (pH˜3), water and brine. The organic layer was dried over magnesium sulphate filtered and excess ethyl acetate was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to column flash chromatography (silica gel; gradient, 50/50 to 25/75 v/v hexane/ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 60 (400 mg, quantitative). LC/MS, 3.32 min (ES+) m/z (relative intensity) 794.18 ([M+H]⁺, 100). 25 ¹H NMR (400 MHz, CDCl₃) δ 8.53 (s, 1H), 8.02 (s, 1H), 7.44 (d, J=7.6 Hz, 2H), 7.21 (s, 1H), 7.08 (d, J=8.2 Hz, 2H), 6.72-6.61 (m, J=8.9 Hz, 2H), 6.16 (s, 1H), 5.97-5.79 (m, J=24.4, 7.5 Hz, 2H), 5.41-5.08 (m, 5H), 4.86 (d, J=12.5 Hz, 1H), 4.69-4.60 (m, 1H), 4.57 (s, 1H), 4.03 (t, J=6.7 Hz, 1H), 3.87 (s, 3H), 3.74 (td, J=9.6, 3.6 Hz, 1H), 2.43-2.09 (m, J=34.8, 19.4, 11.7 Hz, 3H), 1.76 (s, 3H), 1.43 (d, J=6.9 Hz, 3H), 1.30-1.21 (m, 3H), 0.97 (d, J=6.7 Hz, 3H), 0.92 (t, J=8.4 Hz, 3H), 0.84 (s, 9H), 0.23 (s, 3H), 0.12 (s, 3H).

(iv) (11S,11aS)-4-((2S,5S)-37-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-5-isopropyl-2-methyl-4,7,35-trioxo-10,13,16,19,22,25,28,31-octaoxa-3,6,34-triazaheptatriacontanamido)benzyl 11-hydroxy-7-methoxy-8-((5-(((S)-7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (64)

(a) (11S)-allyl 8-((5-(((11S)-10-(((4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl)oxy)carbonyl)-1-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-11-((tert-butyldimethylsilyl)oxy)-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (61)

Potassium carbonate (70 mg, 0.504 mmol, 1 eq) was added to a solution of 55 (370 mg, 0.552 mmol, 1.2 eq) and phenol 60 (400 mg, 0.504 mmol) in dry acetone (25 mL). The reaction was stirred 8 hours at 70° C. The LC/MS showed that all the starting material was not consumed, so the reaction was allowed to stir overnight at room temperature and stirred for an additional 2 hours the next day. Acetone was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 80% ethyl acetate in hexane to 100% ethyl acetate). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give the product 61 (385 mg, 57%). LC/MS, 4.07 min (ES+) m/z (relative intensity) 1336.55 ([M+H]⁺, 50).

(b) (11S)-allyl 8-((5-(((11S)-10-(((4-(2-(1-((1-(allyloxy)-4-methyl-1,2-dioxopentan-3-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl)oxy)carbonyl)-11-hydroxy-7-methoxy-2-methyl-5-oxo-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-11-hydroxy-7-methoxy-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (62)

Tetra-n-butylammonium fluoride (1M, 0.34 mL, 0.34 mmol, 2 eq) was added to a solution of 61 (230 mg, 0.172 mmol) in dry tetrahydrofuran (3 mL). The starting material was totally consumed after 10 minutes. The reaction mixture was diluted with ethyl acetate (30 mL) and washed sequentially with water and brine. The organic phase was dried over magnesium sulphate filtered and excess ethyl acetate removed by rotary evaporation under reduced pressure. The resulting residue 62 was used as a crude mixture for the next reaction. LC/MS, 2.87 min (ES+) m/z (relative intensity) 1108.11 ([M+H]⁺, 100).

(c) (11S)-4-(2-(1-((1-amino-3-methyl-1-oxobutan-2-yl)amino)-1-oxopropan-2-yl)hydrazinyl)benzyl 11-hydroxy-7-methoxy-8-((5-((7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (63)

Tetrakis(triphenylphosphine)palladium(0) (12 mg, 0.01 mmol, 0.06 eq) was added to a solution of crude 62 (0.172 mmol) and pyrrolidine (36 μL, 0.43 mmol, 2.5 eq) in dry dichloromethane (10 mL). The reaction mixture was stirred 20 minutes and diluted with dichloromethane and washed sequentially with saturated aqueous ammonium chloride and brine. The organic phase was dried over magnesium sulphate filtered and excess dichloromethane removed by rotary evaporation under reduced pressure. The resulting residue 63 was used as a crude mixture for the next reaction. LC/MS, 2.38 min (ES+) m/z (relative intensity) 922.16 ([M+H]⁺, 40).

(d) (11S,11aS)-4-((2S,5S)-37-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-5-isopropyl-2-methyl-4,7,35-trioxo-10,13,16,19,22,25,28,31-octaoxa-3,6,34-triazaheptatriacontanamido)benzyl 11-hydroxy-7-methoxy-8-((5-(((S)-7-methoxy-2-methyl-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)pentyl)oxy)-2-methyl-5-oxo-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (64)

1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide (EDCl, 33 mg, 0.172 mmol) was added to a solution of crude 63 (0.172 mmol) and Mal-(PEG)₈-acid (100 mg, 0.172 mmol) in dry dichloromethane (10 mL). The reaction was stirred for 2 hours and the presence of starting material was no longer observed by LC/MS. The reaction was diluted with dichloromethane and washed sequentially with water and brine. The organic phase was dried over magnesium sulphate filtered and excess dichloromethane removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 100% chloroform to 10% methanol in chloroform). Pure fractions were collected and combined and excess eluent was removed by rotary evaporation under reduced pressure to give 64 (E) (60 mg, 25% over 3 steps).

Example 8

Compound 65 is compound 79 of WO 2011/130598

(11S)-4-(1-iodo-20-isopropyl-23-methyl-2,18,21-trioxo-6,9,12,15-tetraoxa-3,19,22-triazatetracosanamido)benzyl 11-hydroxy-7-methoxy-8-(3-((7-methoxy-5-oxo-2-((E)-prop-1-en-1-yl)-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-5-oxo-2-((E)-prop-1-en-1-yl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (66)

N,N′-diisopropylcarbodiimide (DIC, 4.71 μL, 0.0304 mmol) was added to a solution of amine 65 (0.0276 mmol) and Iodo-(PEG)₄-acid (13.1 mg, 0.0304 mmol) in dry dichloromethane (0.8 mL). The reaction was stirred for 3 hours and the presence of starting material was no longer observed by LC/MS. The reaction mixture was directly loaded onto a thin-layer chromatography (TLC) plate and purified by prep-TLC (10% methanol in chloroform). Pure bands were scraped off the TLC plate, taken up in 10% methanol in chloroform, filtered and excess eluent removed by rotary evaporation under reduced pressure to give 66 (D) (20.9 mg, 56%). LC/MS, method 2, 3.08 min (ES+) m/z (relative intensity) 1361.16 ([M+H]⁺, 100).

General Experimental Methods for Example 9

LCMS data were obtained using an Agilent 1200 series LC/MS with an Agilent 6110 quadrupole MS, with Electrospray ionisation. Mobile phase A—0.1% Acetic acid in water. Mobile Phase B—0.1% in acetonitrile. Flow rate of 1.00 ml/min. Gradient from 5% B rising up to 95% B over 3 minutes, remaining at 95% B for 1 minute and then back down to 5% B over 6 seconds. The total run time is 5 minutes. Column: Phenomenex Gemini-NX 3 μm C18, 30×2.00 mm. Chromatograms based on UV detection at 254 nm. Mass Spectra were achieved using the MS in positive mode. Proton NMR chemical shift values were measured on the delta scale at 400 MHz using a Bruker AV400. The following abbreviations have been used: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad. Coupling constants are reported in Hz. Unless otherwise stated, column chromatography (by the flash procedure) were performed on Merck Kieselgel silica (Art. 9385). Mass spectroscopy (MS) data were collected using a Waters Micromass LCT instrument coupled to a Waters 2795 HPLC separations module. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄). All other chemicals and solvents were purchased from Sigma-Aldrich or Fisher Scientific and were used as supplied without further purification.

Optical rotations were measured on an ADP 220 polarimeter (Bellingham Stanley Ltd.) and concentrations (c) are given in g/100 mL. Melting points were measured using a digital melting point apparatus (Electrothermal). IR spectra were recorded on a Perkin-Elmer Spectrum 1000 FT IR Spectrometer. ¹H and ¹³C NMR spectra were acquired at 300 K using a Bruker Avance NMR spectrometer at 400 and 100 MHz, respectively. Chemical shifts are reported relative to TMS (δ=0.0 ppm), and signals are designated as s (singlet), d (doublet), t (triplet), dt (double triplet), dd (doublet of doublets), ddd (double doublet of doublets) or m (multiplet), with coupling constants given in Hertz (Hz). Mass spectroscopy (MS) data were collected using a Waters Micromass ZQ instrument coupled to a Waters 2695 HPLC with a Waters 2996 PDA. Waters Micromass ZQ parameters used were: Capillary (kV), 3.38; Cone (V), 35; Extractor (V), 3.0; Source temperature (° C.), 100; Desolvation Temperature (° C.), 200; Cone flow rate (L/h), 50; De-solvation flow rate (L/h), 250. High-resolution mass spectroscopy (HRMS) data were recorded on a Waters Micromass QTOF Global in positive W-mode using metal-coated borosilicate glass tips to introduce the samples into the instrument. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄), and flash chromatography utilised silica gel (Merck 60, 230-400 mesh ASTM). Except for the HOBt (NovaBiochem) and solid-supported reagents (Argonaut), all other chemicals and solvents were purchased from Sigma-Aldrich and were used as supplied without further purification. Anhydrous solvents were prepared by distillation under a dry nitrogen atmosphere in the presence of an appropriate drying agent, and were stored over 4 Å molecular sieves or sodium wire. Petroleum ether refers to the fraction boiling at 40-60° C.

General LC/MS conditions: The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B over 1.0 min then 5% B to 95% B within 3 min. The composition was held for 0.5 min at 95% B, and then returned to 5% B in 0.3 minutes. Total gradient run time equals 5 min. Flow rate 3.0 mL/min, 400 μL was split via a zero dead volume tee piece which passes into the mass spectrometer. Wavelength detection range: 220 to 400 nm. Function type: diode array (535 scans). Column: Phenomenex® Onyx Monolithic C₁₈ 50×4.60 mm

Example 9 (i) Key Intermediates

(a)

(a-i) (S)-2-(allyloxycarbonylamino)-3-methylbutanoic Acid (12)

Allyl chloroformate (36.2 ml, 340.59 mmol, 1.2 eq) was added dropwise to a stirred solution of L-valine (11)(33.25 g, 283.82 mmol, 1.0 eq) and potassium carbonate (59.27 g, 425.74 mmol, 1.5 eq) in water (650 mL) and THF (650 mL). The reaction mixture was stirred at room temperature for 18 hours, then the solvent was concentrated under reduced pressure and the remaining solution extracted with diethyl ether (3×100 mL). The aqueous portion was acidified to pH 2 with conc. HCl and extracted with DCM (3×100 mL). The combined organics were washed with brine, dried over MgSO₄, filtered and concentrated under reduced pressure to afford the product as a colourless oil (57.1 g, assumed 100% yield). LC/MS (1.966 min (ES⁺)), m/z: 202.1 [M+H]⁺. ¹H NMR (400 MHz, DMSO-d₆) δ 12.57 (br s, 1H), 7.43 (d, 1H, J=8.6 Hz), 5.96-5.86 (m, 1H), 5.30 (ddd, 1H, J=17.2, 3.4, 1.7 Hz), 5.18 (ddd, 1H, J=10.4, 2.9, 1.6 Hz), 4.48 (dt, 2H, J=5.3, 1.5 Hz), 3.85 (dd, 1H, J=8.6, 6.0 Hz), 2.03 (oct, 1H, J=6.6 Hz), 0.89 (d, 3H, J=6.4 Hz), 0.87 (d, 3H, J=6.5 Hz).

(a-ii) (S)-2,5-dioxopyrrolidin-1-yl 2-(allyloxycarbonylamino)-3-methylbutanoate (13)

To a stirred solution of the protected acid 12 (60.6 g, 301.16 mmol, 1.0 eq) and N-hydroxysuccinimide (34.66 g, 301.16 mmol, 1.0 eq) in dry THF (800 mL) was added dicyclohexylcarbodiimide (62.14 g, 301.16 mmol, 1 eq). The reaction was stirred for 18 hours at room temperature. The reaction mixture was then filtered, the solid washed with THF and the combined filtrate was concentrated under reduced pressure. The residue was re-dissolved in DCM and left to stand at 0° C. for 30 minutes. The suspension was filtered and washed with cold DCM. Concentration of the filtrate under reduced pressure afforded the product as a viscous colourless oil (84.7 g, assumed 100% yield) which was used in the next step without further purification. LC/MS (2.194 min (ES⁺)), m/z: 321.0 [M+Na]⁺. ¹H NMR (400 MHz, DMSO-d₆) δ 8.0 (d, 1H, J=8.3 Hz), 5.97-5.87 (m, 1H), 5.30 (ddd, 1H, J=17.2, 3.0, 1.7 Hz), 5.19 (ddd, 1H, J=10.4, 2.7, 1.4 Hz), 4.52 (dt, 2H, J=5.3, 1.4 Hz), 4.32 (dd, 1H, J=8.3, 6.6 Hz), 2.81 (m, 4H), 2.18 (oct, 1H, J=6.7 Hz), 1.00 (d, 6H, J=6.8 Hz),

(a-iii) (S)-2-((S)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanoic Acid (14)

A solution of succinimide ester I3 (12.99 g, 43.55 mmol, 1.0 eq) in THF (50 mL) was added to a solution of L-alanine (4.07 g, 45.73 mmol, 1.05 eq) and NaHCO₃ (4.02 g, 47.90 mmol, 1.1 eq) in THF (100 mL) and H₂O (100 mL). The mixture was stirred at room temperature for 72 hours when the THF was removed under reduced pressure. The pH was adjusted to 3-4 with citric acid to precipitate a white gum. After extraction with ethyl acetate (6×150 mL), the combined organics were washed with H₂O (200 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. Trituration with diethyl ether afforded the product as a white powder which was collected by filtration and washed with diethyl ether (5.78 g, 49%). LC/MS (1.925 min (ES⁺)), m/z: 273.1 [M+H]⁺. ¹H NMR (400 MHz, DMSO-d₆) δ 12.47 (br s, 1H), 8.17 (d, 1H, J=6.8 Hz), 7.16 (d, 1H, J=9.0 Hz), 5.95-5.85 (m, 1H), 5.29 (dd, 1H, J=17.2, 1.7 Hz), 5.17 (dd, 1H, J=10.4, 1.5 Hz), 4.46 (m, 2H), 4.18 (quin, 1H, J=7.2 Hz), 3.87 (dd, 1H, J=9.0, 7.1 Hz), 1.95 (oct, 1H, J=6.8 Hz), 1.26 (d, 3H, J=7.3 Hz), 0.88 (d, 3H, J=6.8 Hz), 0.83 (d, 3H, J=6.8 Hz).

(a-iv) Allyl(S)-1-((S)-1-(4-(hydroxymethyl)phenylamino)-1-oxopropan-2-ylamino)-3-methyl-1-oxobutan-2-ylcarbamate (15)

EEDQ (5.51 g, 22.29 mmol, 1.05 eq) was added to a solution of p-aminobenzyl alcohol (2.74 g, 22.29 mmol, 1.05 eq) and acid 14 (5.78 g, 21.23 mmol, 1 eq) in dry THF (100 mL). and stirred at room temperature for 72 hours. The reaction mixture was then concentrated under reduced pressure and the resulting brown solid was triturated with diethyl ether and filtered with subsequent washing with an excess of diethyl ether to afford the product as an off-white solid (7.1 g, 88%). LC/MS (1.980 min (ES⁺)), m/z: 378.0 [M+H]⁺. ¹H NMR (400 MHz, DMSO-d₆) δ 9.89 (br s, 1H), 8.13 (d, 1H, J=7.0 Hz), 7.52 (d, 2H, J=8.5 Hz), 7.26 (m, 1H), 7.23 (d, 2H, J=8.5 Hz), 5.91 (m, 1H), 5.30 (m, 1H), 5.17 (m, 1H), 4.46 (m, 2H), 5.09 (t, 1H, J=5.6 Hz), 4.48 (m, 2H), 4.42 (m, 3H), 3.89 (dd, 1H, J=8.6, 6.8 Hz), 1.97 (m, 1H), 1.30 (d, 3H, J=7.1 Hz), 0.88 (d, 3H, J=6.8 Hz), 0.83 (d, 3H, J=6.7 Hz).

(b)

1-iodo-2-oxo-6,9,12,15-tetraoxa-3-azaoctadecan-18-oic Acid (17)

A solution of iodoacetic anhydride (0.250 g, 0.706 mmol, 1.1 eq) in dry DCM (1 mL) was added to amino-PEG₍₄₎-acid 16 (0.170 g, 0.642 mmol, 1.0 eq) in DCM (1 mL). The mixture was stirred in the dark at room temperature overnight. The reaction mixture was washed with 0.1 M HCl, water, dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 3% MeOH and 0.1% formic acid in chloroform to 10% MeOH and 0.1% formic acid in chloroform) to afford the product as an orange oil (0.118 g, 42%). LC/MS (1.623 min (ES⁺)), m/z: 433.98 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.069 (s, 1H), 7.22 (br s, 1H), 3.79 (t, 2H, J=5.8 Hz), 3.74 (s, 2H), 3.72-3.58 (m, 14H), 3.50-3.46 (m, 2H), 2.62 (t, 2H, J=5.8 Hz).

(ii) (11S,11aS)-allyl 11-(tert-butyldimethylsilyloxy)-8-(3-iodopropoxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (74)

(a) (S)-5-((tert-butyldimethylsilyloxy)methyl)-1-(5-methoxy-2-nitro-4-(triisopropylsilyloxy)benzoyl)-4,5-dihydro-1H-pyrrol-3-yl trifluoromethanesulfonate (47)

Triflic anhydride (28.4 g, 100.0 mmol, 3.0 eq) was added dropwise, over 25 mins, to a vigorously stirred solution of the ketone 46 (19.5 g, 30.0 mmol, 1.0 eq) in DCM (550 mL) containing 2,6-lutidine (14.4 g, 130.0 mmol, 4.0 eq) at −50° C. The reaction mixture was stirred for 1.5 hours when LC/MS indicated complete reaction. The organic phase was washed successively with water (100 mL), saturated sodium bicarbonate (150 mL), brine (50 mL), and the organic phase was dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 90/10 v/v n-hexane/EtOAc) to afford the product as a pale yellow oil (19.5 g, 82%). LC/MS (4.391 min (ES⁺)), m/z: 713.25 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.68 (s, 1H), 6.72 (s, 1H), 6.02 (t, 1H, J=1.9 Hz), 4.75 (m, 1H), 4.05 (m, 2H), 3.87 (s, 3H), 3.15 (ddd, 1H, J=16.2, 10.3, 2.3 Hz), 2.96 (ddd, 1H, J=16.2, 4.0, 1.6 Hz), 1.28-1.21 (m, 3H), 1.07 (d, 18H, J=7.2 Hz), 0.88 (s, 9H), 0.09 (s, 3H), 0.08 (s, 3H).

(b) (S,E)-(2-((tert-butyldimethylsilyloxy)methyl)-4-(prop-1-enyl)-2,3-dihydro-1H-pyrrol-1-yl)(5-methoxy-2-nitro-4-(triisopropylsilyloxy)phenyl)methanone (67)

Tetrakis(triphenylphosphine)palladium(0) (0.41 g, 0.35 mmol, 0.03 eq) was added to a mixture of the triflate 47 (8.4 g, 11.8 mmol, 1.0 eq), E-1-propene-1-ylboronic acid (1.42 g, 16.5 mmol, 1.4 eq) and potassium phosphate (5.0 g, 23.6 mmol, 2.0 eq) in dry dioxane (60 mL) under a nitrogen atmosphere. The mixture was stirred at 25° C. for 120 mins when LC/MS indicated complete reaction. Ethyl acetate (120 mL) and water (120 mL) were added, the organic phase was removed, washed with brine (20 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 95/5 v/v n-hexane/EtOAc to 90/10 v/v n-hexane/EtOAc) to afford the product as a yellow foam (4.96 g, 70%). LC/MS (4.477 min (ES⁺)), m/z: 605.0 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.67 (s, 1H), 6.74 (s, 1H), 5.93 (d, 1H, J=15.4 Hz), 5.67 (s, 1H), 4.65 (m, 1H), 4.04 (m, 2H), 3.86 (s, 3H), 2.85 (m, 1H), 2.71 (m, 1H), 1.72 (dd, 3H, J=6.8, 1.0 Hz), 1.30-1.22 (m, 3H), 1.07 (d, 18H, J=7.2 Hz), 0.87 (s, 9H), 0.08 (s, 3H), 0.07 (s, 3H).

(c) (S,E)-(2-amino-5-methoxy-4-(triisopropylsilyloxy)phenyl) (2-((tert-butyldimethylsilyloxy)methyl)-4-(prop-1-enyl)-2,3-dihydro-1H-pyrrol-1-yl)methanone (68)

Zinc dust (22.0 g, 0.33 mol, 37 eq) was added, in portions over 20 mins, to a solution of the propenyl intermediate 67 (5.5 g, 9.1 mmol, 1.0 eq) in 5% v/v formic acid/ethanol (55 mL), using an ice bath to maintain the temperature between 25-30° C. After 30 mins, the reaction mixture was filtered through a short bed of Celite®. The Celite® was washed with ethyl acetate (65 mL) and the combined organics were washed successively with water (35 mL), saturated sodium bicarbonate (35 mL) and brine (10 mL). The organic phase was dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 90/10 v/v n-hexane/EtOAc) to afford the product as a pale yellow oil (3.6 g, 69.0%). LC/MS (4.439 min (ES⁺)), m/z: 575.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 6.75 (m, 1H), 6.40 (br s, 1H), 6.28 (m, 1H), 6.11 (d, 1H, J=15.4 Hz), 5.53 (m, 1H), 4.67 (m, 1H), 4.36 (m, 2H), 3.93 (br s, 1H), 3.84 (br s, 1H), 3.73 (s, 3H), 2.86 (dd, 1H, J=15.7, 10.4 Hz), 2.73 (dd, 1H, J=15.9, 4.5 Hz), 1.80 (dd, 3H, J=6.8, 1.3 Hz), 1.35-1.23 (m, 3H), 1.12 (d, 18H, J=7.3 Hz), 0.89 (s, 9H), 0.08 (s, 3H), 0.07 (s, 3H).

(d) (S,E)-allyl 2-(2-((tert-butyldimethylsilyloxy)methyl)-4-(prop-1-enyl)-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-(triisopropylsilyloxy)phenylcarbamate (69)

Allyl chloroformate (0.83 g, 6.88 mmol, 1.1 eq) was added to a solution of the amine 68 (3.6 g, 6.26 mmol, 1.0 eq) in dry DCM (80 mL) containing dry pyridine (1.09 g, 13.77 mmol, 2.2 eq) at −78° C. The dry ice was removed and the reaction mixture allowed to warm to room temperature. After stirring for a further 15 minutes, LC/MS indicated complete reaction. The organic phase was washed successively with 0.01N HCl (50 mL), saturated sodium bicarbonate (50 mL), brine (10 mL), dried over MgSO₄, filtered and concentrated under reduced pressure to leave a pale yellow oil which was used in the next step without further purification (4.12 g, assumed 100% yield). LC/MS (4.862 min (ES⁺)), m/z: 659.2 [M+H]⁺.

(e) (S,E)-allyl 2-(2-(hydroxymethyl)-4-(prop-1-enyl)-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-(triisopropylsilyloxy)phenylcarbamate (70)

The crude intermediate 69 (assumed 100% yield, 4.12 g, 6.25 mmol, 1.0 eq) was dissolved in a mixture of acetic acid (70 mL), methanol (10 mL), THF (10 mL) and water (20 mL) and allowed to stir at room temperature. After 6 hours the reaction mixture was diluted with ethyl acetate (500 mL) and washed successively with water (2×500 mL), saturated sodium bicarbonate (300 mL) and brine (50 mL). The organic phase was dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 1/99 v/v methanol/DCM to 5/95 v/v methanol/DCM) to afford the product as a yellow oil and a further 1 g of unreacted starting material was recovered. This material was subjected to the same reaction conditions as above, but was left stirring for 16 h. After work up and purification, additional product was isolated (2.7 g, 79%, 2 steps) LC/MS (3.742 min (ES⁺)), m/z: 545.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.38 (m, 1H), 7.72 (m, 1H), 6.81 (s, 1H), 6.37 (m, 1H), 6.10 (d, 1H, J=15.8 Hz), 5.97 (m, 1H), 5.53 (m, 1H), 5.36 (ddd, 1H, J=17.2, 3.1, 1.5 Hz), 5.25 (ddd, 1H, J=10.4, 2.5, 1.3 Hz), 4.78 (m, 1H), 4.65 (dt, 2H, J=5.7, 1.3 Hz), 3.84 (m, 3H), 3.79 (s, 3H), 3.04 (dd, 1H, J=16.7, 10.5 Hz), 2.40 (dd, 1H, J=16.0, 4.5 Hz), 1.82 (dd, 3H, J=6.8, 1.0 Hz), 1.36-1.26 (m, 3H), 1.14 (d, 18H, J=7.3 Hz).

(f) (11S,11aS)-allyl 11-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-8-(triisopropylsilyloxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10 (5H)-carboxylate (71)

Dry dimethyl sulfoxide (1.16 g, 14.87 mmol, 3.0 eq) was added dropwise to a solution of oxalyl chloride (0.94 g, 7.43 mmol, 1.5 eq) in DCM (25 mL) at −78° C. under an atmosphere of nitrogen. Maintaining the temperature at −78° C., after 10 mins a solution of the primary alcohol 70 (2.7 g, 4.96 mmol, 1.0 eq) in DCM (20 mL) was added dropwise. After a further 15 mins, dry triethylamine (2.5 g, 24.78 mmol, 5.0 eq) was added, and the reaction mixture allowed to warm to room temperature. The reaction mixture was washed successively with cold 0.1N HCl (50 mL), saturated sodium hydrogen carbonate (50 mL) and brine (10 mL) and the organic layer was dried over MgSO₄, filtered and concentrated under reduced pressure to afford the product as a yellow oil which was used in the next step without further purification (2.68 g, assumed 100% yield). LC/MS (3.548 min (ES⁺)), m/z: 543.2 [M+H]⁺.

(g) (11S,11aS)-allyl 11-(tert-butyldimethylsilyloxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-8-(triisopropylsilyloxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (72)

Tert-butyldimethylsilyltrifluoromethane sulfonate (3.93 g, 14.87 mmol, 3.0 eq) was added to a solution of the carbinolamine 71 (assumed 100% yield, 2.68 g, 4.96 mmol, 1.0 eq) and 2,6-lutidine (2.12 g, 19.83 mmol, 4.0 eq) in dry DCM (40 mL) at 0° C. under an atmosphere of nitrogen. After 10 minutes, the reaction mixture was allowed to warm to room temperature and stirred for a further 60 minutes. The organic phase was washed successively with water (10 mL), saturated sodium bicarbonate (10 mL) and brine (5 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, chloroform to 2/98 v/v Methanol/chloroform) to afford the product as a yellow oil (2.0 g, 63%, 2 steps). LC/MS (4.748 min (ES⁺)), m/z: 657.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.19 (s, 1H), 6.86 (m, 1H), 6.66 (s, 1H), 6.22 (d, 1H, J=15.4 Hz), 5.81 (d, 1H, J=8.8 Hz), 5.78 (m, 1H), 5.48 (m, 1H), 5.11 (d, 1H, J=5.0 Hz), 5.08 (m, 1H), 4.58 (dd, 1H, J=13.4, 5.4 Hz), 4.35 (dd, 1H, J=13.2, 5.7 Hz), 3.83 (s, 3H), 3.76 (s, 1H), 3.00 (dd, 1H, J=15.6, 11.0 Hz), 2.53 (m, 1H), 1.81 (dd, 3H, J=6.8, 0.9 Hz), 1.30-1.18 (m, 3H), 1.08 (d, 9H, J=2.3 Hz), 1.06 (d, 9H, J=2.3 Hz), 0.86 (s, 9H), 0.25 (s, 3H), 0.18 (s, 3H).

(h) (11S,11aS)-allyl 11-(tert-butyldimethylsilyloxy)-8-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (73)

Lithium acetate dihydrate (0.31 g, 3.04 mmol, 1.0 eq) was added to a solution of the diazepine 72 (2.0 g, 3.04 mmol, 1.0 eq) in wet DMF (20 mL) at 25° C. and stirred for 4 hours. The reaction mixture was diluted with ethyl acetate (200 mL) and washed successively with 0.1M citric acid (50 mL, pH 3), water (50 mL) and brine (10 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 50/50 v/v n-hexane/EtOAc to 25/75 v/v n-hexane/EtOAc) to afford the product as a pale yellow solid (0.68 g, 45%). LC/MS (3.352 min (ES⁺)), m/z: 501.1 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.02 (s, 1H), 6.66 (m, 1H), 6.53 (s, 1H), 6.03 (d, 1H, J=15.5 Hz), 5.80 (s, 1H), 5.63 (d, 1H, J=8.9 Hz), 5.55 (m, 1H), 5.29 (m, 1H), 4.87 (m, 2H), 4.39 (dd, 1H, J=13.5, 4.2 Hz), 4.20 (dd, 1H, J=13.2, 5.7 Hz), 3.73 (s, 3H), 3.59 (m, 1H), 2.81 (dd, 1H, J=16.1, 10.5 Hz), 2.35 (d, 1H, J=15.7 Hz), 1.61 (d, 3H, J=6.4 Hz), 0.67 (s, 9H), 0.05 (s, 3H), 0.00 (s, 3H).

(i) (11S,11aS)-allyl 11-(tert-butyldimethylsilyloxy)-8-(3-iodopropoxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (74)

Diiodopropane (0.295 g, 1.00 mmol, 5.0 eq) and potassium carbonate (0.028 g, 0.20 mmol, 1.0 eq) were added to a solution of the phenol 33 (0.100 g, 0.020 mmol, 1.0 eq) in dry acetone (5 mL). The reaction mixture was heated at 60° C. for 6 hours when LC/MS showed complete reaction. The reaction mixture was concentrated to dryness under reduced pressure and the residue was purified by flash chromatography (silica gel, 75/25 v/v n-hexane/EtOAc to 50/50 v/v n-hexane/EtOAc) to afford the product as a colourless oil (0.074 g, 56%). LC/MS (3.853 min (ES⁺)), m/z: 669.0 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.26 (s, 1H), 6.90 (s, 1H), 6.68 (s, 1H), 6.24 (d, 1H, J=15.3 Hz), 5.87 (d, 1H, J=8.9 Hz), 5.78 (m, 1H), 5.53 (m, 1H), 5.12 (m, 2H), 4.65 (m, 2H), 4.41 (m, 1H), 4.11 (m, 1H), 3.93 (s, 3H), 3.81 (m, 1H), 3.40 (t, 2H, J=6.7 Hz), 3.05 (dd, 1H, J=16.3, 10.1 Hz), 2.57 (m, 1H), 2.34 (m, 2H), 1.84 (d, 3H, J=6.6 Hz), 0.92 (s, 9H), 0.28 (s, 3H), 0.26 (s, 3H).

(iii) (11S,11aS)-4-((S)-2-((S)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyl 11-(tert-butyldimethylsilyloxy)-8-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate 79)

(a) Allyl((S)-1-(((S)-1-((4-((((2-((S)-2-(((tert-butyldimethylsilyl)oxy)methyl)-4-((E)-prop-1-en-1-yl)-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamoyl)oxy)methyl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (75)

Triethylamine (0.256 mL, 1.84 mmol, 2.2 eq) was added to a stirred solution of the amine 68 (0.480 g, 0.835 mmol, 1.0 eq) and triphosgene (0.089 g, 0.301 mmol, 0.36 eq) in dry THF (15 mL) at 5° C. (ice bath). The progress of the isocyanate reaction was monitored by periodically removing aliquots from the reaction mixture and quenching with methanol and performing LCMS analysis. Once the isocyanate reaction was complete a solution of Alloc-Val-Ala-PABOH I5 (0.473 g, 1.25 mmol, 1.5 eq) and triethylamine (0.174 mL, 1.25 mmol, 1.5 eq) in dry THF (10 mL) was rapidly added by injection to the freshly prepared isocyanate. The reaction was allowed to stir at 40° C. for 4 hours followed by stirring at room temperature overnight. The mixture was concentrated under reduced pressure, and purified by flash chromatography (silica gel, 20/80 v/v n-hexane/EtOAc to 50/50 v/v n-hexane/EtOAc, then 1/99 v/v DCM/MeOH to 5/95 v/v DCM/MeOH) to afford the product as a yellow solid (0.579 g, 71%). LC/MS (4.468 min (ES⁺)), m/z: 978.55 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.63 (br s, 1H), 8.42 (s, 1H), 7.78 (br s, 1H), 7.53 (d, 2H, J=8.1 Hz), 7.31 (d, 2H, J=8.6 Hz), 6.76 (s, 1H), 6.59 (d, 1H, J=7.6 Hz), 6.36 (brs, 1H), 6.04 (d, 1H, J=15.9 Hz), 5.90 (m, 1H), 5.55 (m, 1H), 5.33-5.21 (m, 3H), 5.10 (s, 2H), 4.66 (m, 2H), 4.57 (dd, 2H, J=5.6, 1.0 Hz), 3.98 (dd, 1H, J=7.3, 6.8 Hz), 3.90 (m, 1H), 3.81 (m, 1H), 3.78 (s, 3H), 2.82 (dd, 1H, J=15.4, 9.6 Hz), 2.72 (dd, 1H, J=15.9, 3.5 Hz), 2.17 (m, 1H), 1.78 (dd, 3H, J=6.5, 0.8 Hz), 1.46 (d, 3H, J=7.1 Hz), 1.29 (m, 3H), 1.11 (d, 18H, J=7.1 Hz), 0.97 (d, 3H, J=6.8 Hz), 0.92 (d, 3H, J=6.8 Hz), 0.83 (s, 9H), 0.04 (s, 3H), 0.01 (s, 3H).

(b) Allyl((S)-1-(((S)-1-((4-((((2-((S)-2-(hydroxymethyl)-4-((E)-prop-1-en-1-yl)-2,3-dihydro-1H-pyrrole-1-carbonyl)-4-methoxy-5-((triisopropylsilyl)oxy)phenyl)carbamoyl)oxy)methyl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (76)

The silyl ether 75 (1.49 g, 1.52 mmol, 1.0 eq) was dissolved in a 7:1:1:2 mixture of acetic acid/methanol/tetrahydrofuran/water (14:2:2:4 mL) and allowed to stir at room temperature. After 2 hours the reaction was diluted with EtOAc (100 mL), washed sequentially with water, aq. sodium bicarbonate then brine. The organic phase was then dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 100/0 then 99/1 to 92/8 v/v DCM/MeOH) to afford the product as an orange solid (1.2 g, 92%). LC/MS (3.649 min (ES⁺)), m/z: 865.44 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.44 (s, 1H), 8.35 (s, 1H), 7.69 (br s, 1H), 7.53 (d, 2H, J=8.7 Hz), 7.32 (d, 2H, J=8.3 Hz), 6.78 (s, 1H), 6.56 (m, 2H), 6.32 (br s, 1H), 6.05 (d, 1H, J=14.9 Hz), 5.90 (m, 1H), 5.56 (m, 1H), 5.30 (m, 2H), 5.22 (m, 1H), 5.10 (d, 2H, J=3.1 Hz), 4.73 (m, 1H), 4.64 (m, 1H), 4.57 (d, 2H, J=5.8 Hz), 4.01 (m, 1H), 3.79 (m, 2H), 3.76 (s, 3H), 2.98 (dd, 1H, J=16.3, 10.2 Hz), 2.38 (dd, 1H, J=16.6, 4.1 Hz), 2.16 (m, 1H), 1.78 (dd, 3H, J=6.8, 0.9 Hz), 1.46 (d, 3H, J=7.1 Hz), 1.29 (m, 3H), 1.11 (d, 18H, J=7.4 Hz), 0.97 (d, 3H, J=6.7 Hz), 0.92 (d, 3H, J=6.8 Hz).

(c) (11S,11aS)-4-((S)-2-((S)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyl 11-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-8-(triisopropylsilyloxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (77)

Dry dimethyl sulfoxide (0.180 g, 2.3 mmol, 3.0 eq) was added dropwise to a solution of oxalyl chloride (0.147 g, 1.1 mmol, 1.5 eq) in DCM (10 mL) at −78° C. under an atmosphere of nitrogen. Maintaining the temperature at −78° C., after 20 minutes, a solution of the primary alcohol 76 (0.666 g, 0.77 mmol, 1.0 eq) in DCM (10 mL) was added dropwise. After a further 15 minutes, dry triethylamine (0.390 g, 3.85 mmol, 5.0 eq) was added, and the reaction mixture allowed to warm to room temperature. The reaction mixture was washed successively with cold 0.1N HCl (10 mL), saturated sodium hydrogen carbonate (10 mL) and brine (5 mL). The organic layer was then dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was then purified by flash chromatography (silica gel, 50/50 v/v n-hexane/EtOAc to 25/75 v/v n-hexane/EtOAc) to afford the product as a white solid (0.356 g, 54%). LC/MS (3.487 min (ES⁺)), m/z: 862.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.34 (br s, 1H), 7.47 (d, 2H, J=7.6 Hz), 7.17 (s, 1H), 7.14 (d, 2H, J=7.5 Hz), 6.86 (br s, 1H), 6.65 (br s, 1H), 6.42 (d, 1H, J=7.6 Hz), 6.22 (d, 1H, J=14.4 Hz), 5.80 (m, 1H), 5.40 (m, 1H), 5.53 (m, 1H), 5.32 (m, 1H), 5.21 (d, 2H, J=9.6 Hz), 5.06 (d, 1H, J=12.3 Hz), 4.90 (m, 1H), 4.58 (m, 3H), 3.98 (m, 1H), 3.84 (m, 1H), 3.81 (s, 3H), 3.50 (m, 1H), 3.05 (dd, 1H, J=16.0, 10.3 Hz), 2.76 (m, 1H), 2.15 (m, 1H), 1.80 (dd, 3H, J=6.7, 0.8 Hz), 1.44 (d, 3H, J=7.1 Hz), 1.16 (m, 3H), 1.01 (d, 18H, J=6.6 Hz), 0.96 (d, 3H, J=6.8 Hz), 0.92 (d, 3H, J=6.8 Hz).

(d) (11S,11aS)-4-((S)-2-((S)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyl 11-(tert-butyldimethylsilyloxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-8-(triisopropylsilyloxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (78)

Tert-butyldimethylsilyltrifluoromethane sulfonate (0.46 g, 1.74 mmol, 3.0 eq) was added to a solution of secondary alcohol 77 (0.5 g, 0.58 mmol, 1.0 eq) and 2,6-lutidine (0.25 g, 2.32 mmol, 4.0 eq) in dry DCM (10 mL) at 0° C. under an atmosphere of nitrogen. After 10 minutes, the reaction mixture was allowed to warm to room temperature and stirred for a further 120 mins. The organic phase was then washed successively with water (10 mL), saturated sodium bicarbonate (10 mL) and brine (5 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 50/50 v/v n-hexane/EtOAc) to afford the product as a white solid (0.320 g, 57%). LC/MS (4.415 min (ES⁺)), m/z: 976.52 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.31 (br s, 1H), 7.48 (d, 2H, J=8.0 Hz), 7.21 (s, 1H), 7.14 (d, 2H, J=8.3 Hz), 6.89 (s, 1H), 6.65 (s, 1H), 6.38 (d, 1H, J=7.3 Hz), 6.25 (d, 1H, J=14.6 Hz), 5.93 (m, 1H), 5.85 (d, 1H, J=8.8 Hz), 5.50 (m, 1H), 5.34 (m, 1H), 5.24 (m, 2H), 5.15 (d, 1H, J=12.5 Hz), 4.86 (d, 1H, J=12.2 Hz), 4.62 (m, 3H), 4.01 (m, 1H), 3.86 (s, 3H), 3.78 (m, 1H), 3.04 (m, 1H), 2.56 (m, 1H), 2.20 (m, 1H), 1.84 (dd, 3H, J=6.6, 0.7 Hz), 1.48 (d, 3H, J=6.8 Hz), 1.20 (m, 3H), 1.05 (d, 9H, J=2.9 Hz), 1.03 (d, 9H, J=2.9 Hz), 0.99 (d, 3H, J=6.8 Hz), 0.95 (d, 3H, J=6.8 Hz), 0.88 (s, 9H), 0.27 (s, 3H), 0.14 (s, 3H).

(e) (11S,11aS)-4-((S)-2-((S)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyl 11-(tert-butyldimethylsilyloxy)-8-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (79)

Lithium acetate dihydrate (0.010 g, 0.10 mmol, 1.0 eq) was added to a solution of the silyl ether 78 (0.100 g, 0.10 mmol, 1.0 eq) in wet DMF (2 mL) at 25° C. for 3 hours. The reaction mixture was then diluted with ethyl acetate (20 mL) and washed successively with 0.1M citric acid (20 mL, pH 3), water (20 mL) and brine (5 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, 5/95 v/v methanol/DCM) to afford the product as a pale yellow oil (0.070 g, 83%). LC/MS (3.362 min (ES⁺)), m/z: 820.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.39 (s, 1H), 7.48 (d, 2H, J=8.2 Hz), 7.25 (s, 1H), 7.12 (d, 2H, J=8.1 Hz), 6.88 (s, 1H), 6.68 (s, 1H), 6.47 (d, 1H, J=7.6 Hz), 6.24 (d, 1H, J=15.2 Hz), 6.03 (s, 1H), 5.92 (m, 1H), 5.84 (d, 1H, J=8.9 Hz), 5.50 (m, 1H), 5.34 (m, 1H), 5.26 (m, 2H), 5.18 (d, 1H, J=12.3 Hz), 4.80 (d, 1H, J=12.4 Hz), 4.66-4.60 (m, 3H), 4.02 (m, 1H), 3.95 (s, 3H), 3.81 (m, 1H), 3.03 (m, 1H), 2.57 (m, 1H), 2.19 (m, 1H), 1.84 (dd, 3H, J=6.8, 0.8 Hz), 1.48 (d, 3H, J=7.1 Hz), 1.00 (d, 3H, J=6.8 Hz), 0.95 (d, 3H, J=6.8 Hz), 0.87 (s, 9H), 0.26 (s, 3H), 0.12 (s, 3H).

(iv) (11S,11aS)-4-((20S,23S)-1-iodo-20-isopropyl-23-methyl-2,18,21-trioxo-6,9,12,15-tetraoxa-3,19,22-triazatetracosanamido)benzyl 11-hydroxy-7-methoxy-8-(3-((S)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yloxy, propoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (66, D)

(a) (11S,11aS)-allyl 8-(3-((11S,11aS)-10-((4-((R)-2-((R)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyloxy)carbonyl)-11-(tert-butyldimethylsilyloxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yloxy)propoxy)-11-(tert-butyldimethylsilyloxy)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (80)

Potassium carbonate (0.030 g, 0.21 mmol, 1.0 eq) was added to a solution of the phenol 79 (0.175 g, 0.21 mmol, 1.0 eq) and the iodo linker 74 (0.214 g, 0.32 mmol, 1.5 eq) in acetone (10 mL). The reaction mixture was heated under a nitrogen atmosphere at 75° C. in a sealed flask for 17 hours. The reaction mixture was concentrated to dryness under reduced pressure and purified by flash chromatography (silica gel, 2/98 v/v methanol/DCM to 5/95 v/v methanol/DCM) to afford the product as a pale yellow solid (0.100 g, 35%). LC/MS (4.293 min (ES⁺)), m/z: 1359.13 [M]+.

(b) (11S,11aS)-allyl 8-(3-((11S,11aS)-10-((4-((R)-2-((R)-2-(allyloxycarbonylamino)-3-methylbutanamido)propanamido)benzyloxy)carbonyl)-11-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yloxy)propoxy)-11-hydroxy-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-1,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (81)

Tetra-n-butylammonium fluoride (1M, 0.22 mL, 0.22 mmol, 2.0 eq) was added to a solution of silyl ether 80 (0.150 g, 0.11 mmol, 1.0 eq) in dry THF (2 mL). The reaction mixture was stirred at room temperature for 20 minutes, after which LC/MS indicated complete reaction. The reaction mixture was diluted with ethyl acetate (10 mL) and washed sequentially with water (5 mL) and brine (5 mL). The organic phase was dried over MgSO₄, filtered and concentrated under reduced pressure to leave a yellow solid. Purification by flash chromatography (silica gel, 6/94 v/v methanol/DCM to 10/90 v/v methanol/DCM) afforded the product as a pale yellow solid (0.090 g, 73%). LC/MS (2.947 min (ES⁺)), m/z: 1154.0 [M+Na]⁺. ¹H NMR (400 MHz, CDCl₃) δ 8.39 (br s, 1H), 7.39 (d, 2H, J=7.6 Hz), 7.18 (d, 2H, J=10.6 Hz), 7.10 (m, 3H), 6.86 (d, 2H, J=10.0 Hz), 6.74 (s, 1H), 6.55 (s, 1H), 6.22 (dd, 2H, J=15.3, 6.6 Hz), 5.85 (m, 2H), 5.74 (m, 3H), 5.52 (m, 2H), 5.22 (m, 1H), 5.00 (m, 2H), 4.57 (m, 6H), 4.41 (m, 2H), 4.09 (m, 4H), 3.85 (m, 11H), 3.06 (m, 2H), 2.76 (m, 2H), 2.20 (m, 2H), 2.08 (m, 1H), 1.79 (d, 6H, J=6.4 Hz), 1.40 (d, 3H, J=6.1 Hz), 0.90 (m, 6H).

(c) (11S,11aS)-4-((R)-2-((R)-2-amino-3-methylbutanamido)propanamido)benzyl 11-hydroxy-7-methoxy-8-(3-((S)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yloxy)propoxy)-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate (65)

Tetrakis(triphenylphospene)palladium(0) (0.005 g, 0.005 mmol, 0.06 eq) was added to a solution of the bis-carbinolamine 81 (0.090 g, 0.08 mmol, 1.0 eq) and pyrrolidine (16 μL, 0.20 mmol, 2.5 eq) in dry DCM (5 mL). After 20 minutes, the reaction mixture was diluted with DCM (10 mL) and washed sequentially with saturated ammonium chloride (5 mL) and brine (5 mL), dried over MgSO₄, filtered and the solvent was removed under reduced pressure to leave the crude product as a pale yellow solid which was used in the next step without further purification (0.075 g, assumed 100% yield). LC/MS (2.060 min (ES⁺)), m/z: 947.2 [M+H]⁺.

(d) (11S,11aS)-4-((20S,23S)-1-iodo-20-isopropyl-23-methyl-2,18,21-trioxo-6,9,12,15-tetraoxa-3,19,22-triazatetracosanamido)benzyl 11-hydroxy-7-methoxy-8-(3-((S)-7-methoxy-5-oxo-2-((E)-prop-1-enyl)-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yloxy)propoxy)-5-oxo-2-((E)-prop-1-enyl)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10 (5H)-carboxylate (66, D)

EDCl (0.015 g, 0.08 mmol, 1.0 eq) was added to a solution of amine 65 (assumed 100% yield 0.075 g, 0.08 mmol, 1.0 eq) and iodoacetamide-PEG₄-acid 17 (0.034 g, 0.08 mmol, 1.0 eq) in dry dichloromethane (5 mL) and the reaction was stirred in the dark. After 50 minutes, a further amount of iodoacetamide-PEG₄-acid 17 (0.007 g, 0.016 mmol, 0.2 eq) was added along with a further amount of EDCl (0.003 g, 0.016 mmol, 0.2 eq). After a total of 2.5 hours, the reaction mixture was diluted with dichloromethane (15 mL) and washed sequentially with water (10 mL) and brine (10 mL). The organic phase was dried over MgSO₄, filtered and concentrated under reduced pressure. The resulting residue was purified by flash chromatography (silica gel, Chloroform 100% to 90:10 v/v Chloroform:Methanol). Pure fractions were combined to afford the product (0.0254 g, 23%, 2 steps). The crude fractions were collected and purified by preparative TLC (silica gel, 90:10 v/v Chloroform:Methanol) to afford a second batch of product (0.0036 g, 3%, 2 steps). LC/MS (2.689 min (ES⁺)), m/z: 681.0 ½[M+2H]+.

Example 10: Activity of Released Compounds

K562 Assay

K562 human chronic myeloid leukaemia cells were maintained in RPM1 1640 medium supplemented with 10% fetal calf serum and 2 mM glutamine at 37° C. in a humidified atmosphere containing 5% CO₂ and were incubated with a specified dose of drug for 1 hour or 96 hours at 37° C. in the dark. The incubation was terminated by centrifugation (5 min, 300 g) and the cells were washed once with drug-free medium. Following the appropriate drug treatment, the cells were transferred to 96-well microtiter plates (10⁴ cells per well, 8 wells per sample). Plates were then kept in the dark at 37° C. in a humidified atmosphere containing 5% CO₂. The assay is based on the ability of viable cells to reduce a yellow soluble tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT, Aldrich-Sigma), to an insoluble purple formazan precipitate. Following incubation of the plates for 4 days (to allow control cells to increase in number by approximately 10 fold), 20 μL of MTT solution (5 mg/mL in phosphate-buffered saline) was added to each well and the plates further incubated for 5 h. The plates were then centrifuged for 5 min at 300 g and the bulk of the medium pipetted from the cell pellet leaving 10-20 μL per well. DMSO (200 μL) was added to each well and the samples agitated to ensure complete mixing. The optical density was then read at a wavelength of 550 nm on a Titertek Multiscan ELISA plate reader, and a dose-response curve was constructed. For each curve, an IC₅₀ value was read as the dose required to reduce the final optical density to 50% of the control value.

Compound RelC has an IC₅₀ of less than 0.1 pM in this assay.

Compound RelE has an IC₅₀ of 0.425 nM in this assay.

Example 11: Formation of Conjugates

General Antibody Conjugation Procedure

Antibodies are diluted to 1-5 mg/mL in a reduction buffer (examples: phosphate buffered saline PBS, histidine buffer, sodium borate buffer, TRIS buffer). A freshly prepared solution of TCEP (tris(2-carboxyethyl)phosphine hydrochloride) is added to selectively reduce cysteine disulfide bridges. The amount of TCEP is proportional to the target level of reduction, within 1 to 4 molar equivalents per antibody, generating 2 to 8 reactive thiols. After reduction for several hours at 37° C., the mixture is cooled down to room temperature and excess drug-linker (A, B, C, D, E) added as a diluted DMSO solution (final DMSO content of up to 10% volume/volume of reaction mixture). The mixture was gently shaken at either 4° C. or room temperature for the appropriate time, generally 1-3 hours. Excess reactive thiols can be reacted with a ‘thiol capping reagent’ like N-ethyl maleimide (NEM) at the end of the conjugation. Antibody-drug conjugates are concentrated using centrifugal spin-filters with a molecular weight cut-off of 10 kDa or higher, then purified by tangential flow filtration (TFF) or Fast Protein Liquid Chromatography (FPLC). Corresponding antibody-drug conjugates can be determined by analysis by High-Performance Liquid Chromatography (HPLC) or Ultra-High-Performance Liquid Chromatography (UHPLC) to assess drug-per-antibody ratio (DAR) using reverse-phase chromatography (RP) or Hydrophobic-Interaction Chromatography (HIC), coupled with UV-Visible, Fluorescence or Mass-Spectrometer detection; aggregate level and monomer purity can be analysed by HPLC or UHPLC using size-exclusion chromatography coupled with UV-Visible, Fluorescence or Mass-Spectrometer detection. Final conjugate concentration is determined by a combination of spectroscopic (absorbance at 280, 214 and 330 nm) and biochemical assay (bicinchonic acid assay BCA; Smith, P. K., et al. (1985) Anal. Biochem. 150 (1): 76-85; using a known-concentration IgG antibody as reference). Antibody-drug conjugates are generally sterile filtered using 0.2 μm filters under aseptic conditions, and stored at +4° C., −20° C. or −80° C.

DAR Determination

Antibody or ADC (ca. 35 μg in 35 μL) was reduced by addition of 10 μL borate buffer (100 mM, pH 8.4) and 5 μL DTT (0.5 M in water), and heated at 37° C. for 15 minutes. The sample was diluted with 1 volume of acetonitrile: water: formic acid (49%: 49%: 2% v/v), and injected onto a Widepore 3.6μ XB-C₁₈ 150×2.1 mm (P/N 00F-4482-AN) column (Phenomenex Aeris) at 80° C., in a UPLC system (Shimadzu Nexera) with a flow rate of 1 ml/min equilibrated in 75% Buffer A (Water, Trifluoroacetic acid (0.1% v/v) (TFA), 25% buffer B (Acetonitrile:water:TFA 90%:10%:0.1% v/v). Bound material was eluted using a gradient from 25% to 55% buffer B in 10 min. Peaks of UV absorption at 214 nm were integrated. The following peaks were identified for each ADC or antibody: native antibody light chain (L0), native antibody heavy chain (H0), and each of these chains with added drug-linkers (labelled L1 for light chain with one drug and H1, H2, H3 for heavy chain with 1, 2 or 3 attached drug-linkers). The UV chromatogram at 330 nm was used for identification of fragments containing drug-linkers (i.e., L1, H1, H2, H3).

A PBD/protein molar ratio was calculated for both light chains and heavy chains:

${\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{light}\mspace{14mu}{chain}} = \frac{\%\mspace{14mu}{Area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{nm}\mspace{14mu}{for}\mspace{14mu} L\; 1}{\%\mspace{14mu}{Area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{nm}\mspace{20mu}{for}\mspace{14mu} L\; 0\mspace{14mu}{and}\mspace{14mu} L\; 1}$ ${\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{heavy}\mspace{14mu}{chain}} = \frac{\sum\limits_{n = 0}^{3}{n \times \left( {\%\mspace{14mu}{area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{nm}\mspace{14mu}{for}\mspace{14mu}{Hn}} \right)}}{{\sum\limits_{n = 0}^{3}{\%\mspace{14mu}{area}\mspace{14mu}{at}\mspace{14mu} 214\mspace{14mu}{for}\mspace{14mu}{Hn}}}\;}$

Final DAR is calculated as:

${DAR} = {2 \times \left( {{\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{light}\mspace{14mu}{chain}} + {\frac{Drug}{Protein}{ratio}\mspace{14mu}{on}\mspace{14mu}{heavy}\mspace{14mu}{chain}}} \right)}$

DAR measurement is carried out at 214 nm because it minimises interference from drug-linker absorbance.

Generation of ADCs

Antibody A (comprising a variable domain which is SEQ ID NO. 1 paired with SEQ ID NO. 2) was conjugated with drug linker A to give Conj A-A, and the DAR was measured to be 2.15 (see table below).

Other ADCs were also prepared, as shown in the table below.

Simulect is an anti-CD25 antibody comprising a VH domain having the sequence according to SEQ ID NO. 1 and a VL domain having the sequence according to SEQ ID NO. 2.

ADCs targeted to CD25 were generated by conjugating Simulect antibodies drug-linker A, as described above. The resulting ADC is listed in the table below. B12 anti-HIV gp120 antibody was used to generate control non-CD25 targeted ADC.

ADC DAR Concentration [mg/ml] Yield [%] Simulect-A 2.15 3.94 71 B12-A 1.94 0.5 49

Example 12: In Vitro Cytotoxicity of ADCs

Cell Culture

SU-DHL-1 and Karpas299 cells were from the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures. Daudi cells were from the American Type Culture Collection. Cell culture medium was RPMI 1640 supplemented with L-Glutamine and 10% FBS. Cells were grown at 37° C., 5% CO₂, in a humidified incubator.

Cytotoxicity Assay

The concentration and viability of cultures of suspended cells (at up to 1×10⁶/ml) were determined by mixing 1:1 with Trypan blue and counting clear (live)/blue (dead) cells with a haemocytometer. The cell suspension was diluted to the required seeding density (generally 10⁵/ml) and dispensed into 96-well flat bottomed plates. For Alamar blue assay, 100 μl/well was dispensed in black-well plates. For MTS assay, 50 μl/well was dispensed in clear-well plates. A stock solution (1 ml) of ADC (20 μg/ml) was made by dilution of filter-sterile ADC into cell culture medium. A set of 8×10-fold dilutions of stock ADC were made in a 24 well plate by serial transfer of 100 μl onto 900 μl of cell culture medium. Each ADC dilution (100 μl/well for Alamar blue, 50 μl/well for MTS) was dispensed into 4 replicate wells of the 96-well plate, containing cell suspension. Control wells received the same volume of culture medium only. After incubation for 4 days, cell viability was measured by either Alamar blue or MTS assay.

AlamarBlue® (Invitrogen, catalogue number DAL1025) was dispensed (20 μl per well) into each well and incubated for 4 hours at 37° C. in the CO₂-gassed incubator. Well fluorescence was measured at excitation 570 nm, emission 585 nm. Cell survival (%) was calculated from the ratio of mean fluorescence in the 4 ADC-treated wells compared to the mean fluorescence in the 4 control wells (100%).

MTS (Promega, catalogue number G5421) was dispensed (20 μl per well) into each well and incubated for 4 hours at 37° C. in the CO₂-gassed incubator. Absorbance was measured at 490 nm. Cell survival (%) was calculated from the mean absorbance in the 4 ADC-treated wells compared to the mean absorbance in the 4 control wells (100%). Dose response curves were generated from the mean data of 3 replicate experiments and the EC₅₀ was determined by fitting data to a sigmoidal dose-response curve with variable slope using Prism (GraphPad, San Diego, Calif.).

Binding of Simulect to CD25 +Ve Cell Lines

Karpas299 and SU-DHL-1 anaplastic large cell lymphoma (ALCL)-derived cell lines have been previously reported to express CD25 (2,3). To confirm their expression profile, CD25 surface expression was analyzed by flow cytometry. Simulect was used as a CD25-specific antibody. B12 was used as a negative control antibody.

FIG. 1 shows expression of CD25 on Karpas299 and SU-DHL-1 cell lines. Surface CD25 expression on Karpas and SU-DHL-1 was determined by flow cytometry. Graphs represent the average of three (Karpas299) or four independent experiments (SU-DHL-1). EC₅₀ values are reported in ng/ml.

Both cell lines specifically bound Simulect but not negative control antibodies, confirming expression of cell surface CD25.

EC₅₀ (ng/ml) Simulect B12 Karpas 45.13 536558 SUDHL1 66.68 1.952e²² In Vitro Cytotoxicity

The efficacy of Simulect-A was tested against SU-DHL-1 cells. As a CD25-negative control, Daudi B cells were used.

FIG. 2 shows in vitro efficacy of Simulect-A. Serial 10-fold dilutions (μg/mL) of Simulect-A were incubated with SU-DHL-1 or Daudi cells. The Alamar Blue assay was performed at the end of the incubation period and cell survival calculated. Graphs represent the average of three replicate experiments.

Simulect-A showed significant cytotoxicity against SU-DHL-1 cells (FIG. 2).

Example 13—In Vivo Anti-Tumour Activity of ADCs

NOD/SCID mice were chosen as the xenograft host for the human anaplastic large cell lymphoma SU-DHL-1 cell line to test the efficacy of a CD25-targeted PBD ADC (Simulect-A, as described above).

Establishment of SU-DHL-1 Xenograft Model

A preliminary study was carried out to establish a suitable xenograft model for the human histiocytic lymphoma (ALCL) SU-DHL-1 cell line. CD1 Nu/Nu (T cell deficient) and NOD/SCID (T and B cell deficient) mice were used for this study. A range of SU-DHL-1 cells concentrations (5×10⁶, 10×10⁶ or 15×10⁶) were inoculated subcutaneously. Three mice were used per cell concentration and per strain.

FIG. 3 shows subcutaneous growth of SU-DHL-1 xenografts in NOD/SCID mice. Graph represents tumor volumes of three NOD/SCID mice subcutaneously injected with 15×10⁶ SU-DHL-1 cells. Tumours volumes were calculated by using the standard formula for determining the volume of an ellipsoid (i.e., [length×width×depth×π]/6).

No tumour growth of subcutaneous xenograft was detected in CD1 Nu/Nu mice at any of the cell concentrations used (not shown) and only at the highest cell concentration (15×10⁶ cells/100 μL RPMI) in NOD/SCID mice, as shown in FIG. 3.

Subcutaneous inoculation of 15×10⁶ SU-DHL-1 cells in 100 μL of non-supplemented RPMI in NOD/SCID mice was selected as the mice xenograft model for subsequent efficacy experiments.

In Vivo Anti-Tumour Study Design

Drugs and Treatment:

Animals per Dose level Dose volume Group No group Test material (mg/kg) (ml/kg) 1 8 Simulect-A 0.3 10 2 8 Simulect-A 1.0 10 Procedures:

-   -   Set up CR female NCr nu/nu mice with I×KARPAS-299-SPN tumor         cells in 0% Matrigel sc in flank.     -   Cell Injection Volume is 0.1 mL/mouse.     -   Age at Start Date: 8 to 12 weeks.     -   Perform a pair match when tumors reach an average size of         100-150 mm³ and begin treatment.     -   Body Weight: qd×5 then bi-wk to end     -   Caliper Measurement: bi-wk to end     -   Report any adverse reactions or death immediately.     -   Any individual animal with a single observation of >30% body         weight loss or three consecutive measurements of >25% body         weight loss will be euthanized.     -   Any group with two measurements of mean body weight loss of >20%         or >10% mortality will stop dosing. The group is not euthanized         and recovery is allowed. Within a group with >20% weight loss,         individuals hitting the individual body weight loss endpoint         will be euthanized. If the group treatment related body weight         loss is recovered to within 10% of the original weights, dosing         may resume at a lower dose or less frequent dosing schedule.         Exceptions to non-treatment body weight % recovery may be         allowed on a case-by-case basis.     -   Endpoint TGD. Animals are to be monitored individually. The         endpoint of the experiment is a tumor volume of 2000 mm³ or 60         days, whichever comes first. Responders can be followed longer.         When the endpoint is reached, the animals are to be euthanized.         General Methodological Approach

For the calculation of group mean tumor volumes the following rule was applied: when an animal exited the study due to tumor size, the final tumor volume recorded for the animal was included with the data used to calculate the mean volume at subsequent time points. Error bars indicate standard error of the mean (SEM). Tumor volumes values were not used to calculate group mean tumor volumes when fewer than 50% of the animals in a group remained in the study. Prism (GraphPad, San Diego, Calif.) was used for graphical presentations and statistical analyses.

Results

FIG. 4 shows antitumor activity of CD25-specific ADCs in the SU-DHL-1 xenograft model. Mice were dosed when the mean tumor volume per experimental group reached 0.1 cm3. Mice were treated with a single dose of the ADC at 0.3 and 1 mg/kg via IV in the tail vein. Data represent the mean tumour volume from eight mice in each group.

Simulect-A showed antitumor activity in the SU-DHL-1 xenograft model. Treatment of mice with CD25-targeted ADCs was not associated with any significant changes in body weight, indicating no major toxic effects.

Abbreviations

-   Ac acetyl -   Acm acetamidomethyl -   Alloc allyloxycarbonyl -   Boc di-tert-butyl dicarbonate -   t-Bu tert-butyl -   Bzl benzyl, where Bzl-OMe is methoxybenzyl and Bzl-Me is     methylbenzene -   Cbz or Z benzyloxy-carbonyl, where Z—Cl and Z—Br are chloro- and     bromobenzyloxy carbonyl respectively -   DMF N,N-dimethylformamide -   Dnp dinitrophenyl -   DTT dithiothreitol -   Fmoc 9H-fluoren-9-ylmethoxycarbonyl -   imp N-10 imine protecting group:     3-(2-methoxyethoxyl)propanoate-Val-Ala-PAB -   MC-OSu maleimidocaproyl-O—N-succinimide -   Moc methoxycarbonyl -   MP maleimidopropanamide -   Mtr 4-methoxy-2,3,6-trimethtylbenzenesulfonyl -   PAB para-aminobenzyloxycarbonyl -   PEG ethyleneoxy -   PNZ p-nitrobenzyl carbamate -   Psec 2-(phenylsulfonyl)ethoxycarbonyl -   TBDMS tert-butyldimethylsilyl -   TBDPS tert-butyldiphenylsilyl -   Teoc 2-(trimethylsilyl)ethoxycarbonyl -   Tos tosyl -   Troc 2,2,2-trichlorethoxycarbonyl chloride -   Trt trityl -   Xan xanthyl

SEQUENCES SEQ ID NO. 1 (Simulect VH): QLQQSGTVLARPGASVKMSCKASGYSFTRYWMHWIKQRPGQGLEWIGAIY PGNSDTSYNQKFEGKAKLTAVTSASTAYMELSSLTHEDSAVYYCSRDYGY YFDFWGQGTTLTVS SEQ ID NO. 2 (Simulect VL): QIVSTQSPAIMSASPGEKVTMTCSASSSRSYMQVVYQQKPGTSPKRWIYD TSKLASGVPARFSGSGSGTSYSLTISSMEAEDAATYYCHQRSSYTFGGGT KLEIK 

The invention claimed is:
 1. A conjugate of formula ConjE:

wherein AB is an antibody that binds to CD25 and comprises a VH domain having the amino acid sequence according to SEQ ID NO:1 paired with a VL domain comprising the amino acid sequence of SEQ ID NO:2; and wherein the drug loading of drugs (D) to antibody (AB) is an integer from 1 to about
 8. 2. The conjugate according to claim 1, wherein the antibody is an intact antibody.
 3. The conjugate according to claim 1, wherein the antibody is humanized, deimmunized, or resurfaced.
 4. The conjugate according to claim 1, wherein the drug loading of drugs (D) to antibody is 1, 2, 3, or
 4. 5. A pharmaceutical composition comprising the conjugate of claim 1 and a pharmaceutically acceptable diluent, carrier, or excipient.
 6. The pharmaceutical composition of claim 5, further comprising a therapeutically effective amount of a chemotherapeutic agent.
 7. A method of treating cancer comprising administering to a patient the pharmaceutical composition of claim
 5. 8. The method of claim 7 wherein the patient is administered a chemotherapeutic agent, in combination with the conjugate. 